A sonic boom has been heard over London and Cambridge after two RAF jets were scrambled to intercept a private plane.
The aircraft was travelling from Germany and had lost communication with air traffic controllers.
It was diverted to Stansted Airport by the Typhoon jets, which took off from RAF Coningsby in Lincolnshire.
Several people reported hearing a "massively loud bang" in London, Cambridge and other areas in the South East.
Posting on Twitter, Alistair Broomhead said: "Just heard a loud boom in E12, windows rattled, sounded like an explosion, anyone else in London hear anything? Know what's going on?"
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Javelin Sam, from Essex, tweeted a doorbell webcam video showing how loud the sonic boom was.
Another user, John Walsh, said: "Sonic boom just now over Cambridge! Blew my window off its casement stay and scared the bloomin' life out of me and the several pigeons outside!"
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Meanwhile, Londoner Jenny Hao said: "Has there been some sort of explosion in #Deptford? Just felt enormous bang whilst walking along the river in Greenwich and saw smoke."
Emma Boswell posted: "I was walking through Waltham Abbey when I heard it. Honestly thought a bomb went off but yeah it was a sonic boom in Cambridge!"
Others posted video of one of the jets flying over Stansted Airport and tracking data showing the aircraft's earlier supersonic speed.
An RAF spokesperson said: "The RAF can confirm Quick Reaction Alert Typhoon aircraft were launched this afternoon from RAF Coningsby to intercept a civilian aircraft that had lost communications; subsequently, communications were re-established, the aircraft was intercepted and safely escorted to Stansted.
"The Typhoon aircraft were authorised to transit at supersonic speed for operational reasons."
The jets are often deployed to escort aircraft that lose contact with air traffic control or don't respond to communications.
The Typhoon can go from brakes off to Mach 1.5 (1150 mph/1852 kmh) in two and a half minutes, according to the RAF.
Its top speed is Mach 1.8 (1381 mph/2222 kmh).
The jet - based at Coningsby and RAF Lossiemouth - can carry air to air missiles and is also compatible GPS and laser-guided Paveway bombs.
Metropolitan Police Commissioner Dame Cressida Dick told BBC Radio 4's Today programme the trip had not been "against the law - that's for sure".
People should go for exercise "from your front door and come back to your front door", she said, adding: "That's my view of local."
The Evening Standard reported that the prime minister had been seen in the Olympic Park, with his security detail, on Sunday.
There's nothing in English lockdown law that says Boris Johnson shouldn't have pedalled around London's Olympic park on Sunday, seven miles from Downing Street.
But this comes at a time when the government is desperately pleading with people to take Covid-19 seriously and follow the rules.
In England that means leaving home only for essential work, shopping and exercise. The guidance also says "stay local" without defining how far people can roam.
Travel for exercise is allowed "a short distance within your area" to access an open space.
Number 10 will insist that's precisely what Mr Johnson did.
But his ride highlights the problem everyone faces trying to interpret rules, and relying on people using common sense.
The outing certainly doesn't help ministers straining to tell the public - in clear, consistent, easy-to-understand terms - to stay at home.
Andy Slaughter, Labour MP for Hammersmith, west London, criticised the prime minister for having a "do-as-I-say, not-as-I-do" attitude.
Speaking to Today, Policing Minister Kit Malthouse said: "What we are asking people to do is when they exercise to stay local.
"Now local is, obviously, open to interpretation, but people broadly know what local means.
"If you can get there under your own steam and you are not interacting with somebody... then that seems perfectly reasonable to me."
Reuters
The issue of travelling for exercise was highlighted at the weekend after police in Derbyshire fined two women £200 after they drove five miles from home to take a walk - a penalty that was later dropped.
Government advice for England says people can leave home to exercise, but adds: "This should be limited to once per day, and you should not travel outside your local area."
The guidance adds: "Stay local means stay in the village, town, or part of the city where you live."
The government also states: "The law is what you must do; the guidance might be a mixture of what you must do and what you should do."
In Scotland, the advice is that exercise can be taken if it "starts and finishes at the same place, which can be up to five miles from the boundary of your local authority area".
In Wales, exercise also has to start from and finish at home. There no limits on distance travelled, although the advice is that "the nearer you stay to your home, the better".
Boris Johnson was spotted cycling seven miles from Downing Street, raising questions as to how far you can go for exercise under lockdown rules.
Government guidance states that people in England should "stay local" when leaving home, which is only allowed for a few essential reasons, including exercise once a day and shopping for basic necessities.
It adds: "Stay local means stay in the village, town, or part of the city where you live."
The PM was seen cycling at the Olympic Park in east London on Sunday, the Evening Standard reported - seven miles from his home in Westminster, and three boroughs away.
Number 10 has refused to reveal whether he cycled there or was driven to the park to cycle.
A spokesman added: "The PM has exercised within the COVID rules and any suggestion to the contrary is wrong."
Image:Boris Johnson, here in 2006, was often seen on his bike around London before he became PM
Does this mean everyone can exercise seven miles from home?
Cycling seven miles and back would not be too long a ride for many cyclists.
But, without a specific distance limit in the rules, this appears to have allowed for different interpretations.
Derbyshire Police were criticised over the weekend for fining two women £200 for driving five miles from home, separately, to go for a walk.
They have now dropped the fine and apologised to the women, but that - and now the PM's cycling - has led to a debate over the guidance.
Image:Jessica Allen (left) and friend Eliza Moore were fined by police in Derbyshire
Metropolitan Police Commissioner Dame Cressida Dick said Mr Johnson's bike ride was not against the law.
However, she told the BBC "local" is a "relative term" and, for her, means "if you can, go for your exercise from your front door and come back to that front door".
Former Liberal Democrat leader Tim Farron's constituency is in the Lake District, where he said police are reporting that people have been travelling hundreds of miles to reach the beauty spot - but he also has constituents asking if they will be fined for driving five minutes to a local park.
He said he has written to the PM calling for clearer guidance on exercise.
Image:Police presence before a proposed anti-lockdown protest in Clapham Common, London
'Shouldn't he stay in Westminster?'
With the rules stating you should stay in your village, town, or part of the city, the PM's seven-mile trip has come under fire.
However, with villages being smaller than towns and parts of cities, does that mean people living in villages have a smaller radius of where they can exercise?
Labour has criticised Mr Johnson's cycle ride, with Hammersmith MP Andy Slaughter saying: "Once again it is 'do as I say, not as I do', from the prime minister."
And a woman who said she saw the PM in the Olympic Park, said she was "shocked to see him cycling around looking so care-free".
She told the PA news agency: "Also, considering he's advising everyone to stay at home and not leave their area, shouldn't he stay in Westminster and not travel to other boroughs?"
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PM: 'Now is the moment for maximum vigilance'
What are the rules in the UK's other nations?
Wales
The country is under Level 4 - equivalent to England's lockdown - with the guidance saying there are no limits on the distance you can travel during exercise, "though the nearer you stay to home, the better".
It says you should start and finish from your home.
But, like in England, there have been incidents where people have been fined for exercising too far from home.
On Saturday, a mother was fined for driving 17 miles to Aber Falls in Snowdonia National Park, where she said there were hardly any other people.
She said she believed she had been following the rules and thought it was better than walking down to the beach near her home, where she said there were about 40 families the following day.
Image:The rules over how far you can exercise from your home during lockdown are not clear enough, some politicians have said
Scotland
The mainland and Skye are under a Level 4 lockdown, which states that you can travel for exercise that starts and finishes at the same place.
But the rules are more specific as they say the place where you start and finish "can be up to five miles from the boundary of your local authority area".
So, as long as you know exactly where the boundary of your local authority area is, you are within the rules if you remain five miles from there.
Image:People in most of Scotland can travel five miles out of their local authority boundary to exercise
Northern Ireland
The rules are slightly more clear in Northern Ireland, which is under a six-week lockdown that started on Boxing Day.
It says you should not travel more than 10 miles from your home to exercise.
If there are crowds when you arrive at the place you want to exercise from, you should find an alternative place, the rules add.
However, it does not say how far you can walk or cycle from that place.
Brush with the law! Moment police raid London barber's shop and catch staff cutting two men's hair despite lockdown ban - before slapping boss with £1,000 fine
City of London police raided The Grooming Lounge Barbers, in Barbican
Footage showed staff cutting two men's hair despite the current restrictions
It comes just weeks after England was plunged into a third national lockdown
This is the moment police catch barber shop staff cutting two men's hair amid the lockdown before hitting the owner with a £1,000 fine for their 'blatant disregard of coronavirus regulations'.
Body-cam footage released by City of London Police shows officers raid The Grooming Lounge Barbers, in Barbican, and catch two customers receiving a haircut from staff despite the current restrictions on January 9.
The scenes come just weeks after England was plunged into a third national lockdown amid the spread of a mutant version of the coronavirus.
Staff inside The Grooming Lounge Barbers, in Barbican, central London, are caught cutting two men's hair on January 9
City of London police enter the barber shop in London which has been covered in old newspapers
During the clip, which was shared by the force on social media, the police enter the barber shop and confront members of staff.
The shop's windows had been covered with old newspapers in an apparent attempt to stop people from seeing they were open.
In a statement the force said: 'City of London Police officers attended a barbershop in the City that was operating despite current restrictions.
'The owner was issued with a £1,000 fine. This is a blatant disregard of coronavirus regulations & won't be tolerated. The message is clear: #StayAtHome.
'Most people are doing their part and obeying the rules to protect the NHS and save lives, but we will continue to deal with those who flout the rules putting everyone at risk.'
It comes after Sainsbury's reinstated bouncers outside its supermarkets to tackle shoppers not wearing a mask after police said they lacked the manpower to enforce the rules.
The chain sent an email to all customers saying guards would 'challenge' maskless customers or people shopping in groups.
An officer enters the shop and speaks with the hairdressers who have breached the coronavirus laws
The officer catches the members of staff cutting hair despite the current restrictions in place
The Grooming Lounge Barbers, in Barbican, was slapped with a £1,000 fine after they were caught by police on January 9
It joins Morrisons, who has also reintroduced security at the doors and vowed to ban anyone refusing to wear a face covering without a medical exemption.
Britain's policing minister Kit Malthouse said police would intervene in serious breaches of Covid rules in shops, but measures imposed and enforced by owners would be effective in most cases.
Meanwhile Brian Booth, chair of West Yorkshire Police Federation, emphasised that officers would only intervene if 'other offences were committed', such as when the customer refusing to wear a mask became violent or abusive.
Mr Booth criticised the current regulations as 'woolly', saying they left too many 'loose ends' which 'cheesed-off' officers had to interpret for themselves.
It came as Met Police Commissioner Cressida Dick said it was 'preposterous' that people would not know the Covid rules, and vowed to continue fining lawbreakers.
Writing in The Times today, Dame Cressida said: 'It is preposterous to me that anyone could be unaware of our duty to do all we can to stop the spread of the virus.
'We have been clear that those who breach Covid-19 legislation are increasingly likely to face fines.
'We will still be engaging, explaining and encouraging but those who break the rules or refuse to comply where they should without good reason will find officers moving much more quickly to enforcement action.'
Meanwhile in Derbyshire, two women who were fined £200 for driving seven miles to Foremark Reservoir for a walk said the police had cancelled their fines following a backlash against an overzealous interpretation of the law.
Jessica Allen and Eliza Moore, both 27, were slapped with the penalties on Wednesday after they were approached by several officers in the park.
Derbyshire Police originally defended the decision to fine the women for breaching Covid rules but Ms Allen today revealed they had received separate calls from the force who apologised to them both and informed them their fines will be scrapped.
Met Police chief Cressida Dick says it is 'preposterous' people could not be aware of coronavirus laws as she vows keep fining people
Britain's most senior police officer said it is 'preposterous' that people could be unaware of the need to follow the third national lockdown and warned that rule-breakers will be fined.
Met Police chief Dame Cressida Dick said people are still holding house parties, meeting in basements to gamble, and attending unlicensed raves despite rising numbers of coronavirus cases and deaths.
She warned that anyone caught breaking the rules or failing to comply would result in officers 'moving much more quickly to enforcement action'.
It comes amid increasing calls for tougher shutdown restrictions, with No10 even considering imposing Chinese-style curfews, outdoor mask mandates and three metre social distancing.
Writing in the Times today, Dame Cressida said: 'It is preposterous to me that anyone could be unaware of our duty to do all we can to stop the spread of the virus. We have been clear that those who breach Covid-19 legislation are increasingly likely to face fines.
'We will still be engaging, explaining and encouraging but those who break the rules or refuse to comply where they should without good reason will find officers moving much more quickly to enforcement action.'
BORIS Johnson will hold a Cabinet meeting of his top team this morning as he considers whether to implement tougher lockdown rules to try and curb Covid case numbers.
Boris Johnson is set to address his team on Zoom todayCredit: AFP or licensors
Shops, schools and sports facilities were shut across England, with people told to stay at home once again - at least until the middle of February.
But case numbers have continued to rise - partly because of people being allowed to mix between households over Christmas, and over the new super-spreading Covid strain.
Hospitals are under significant pressure, and could be overwhelmed within a fortnight, NHS bosses have said.
Government are considering what else might be needed to stop the spread of the virus - though no changes are expected to be imminent.
Brits were last night cautioned against going for takeaway coffees — amid warnings two pals meeting up will be outlawed if people continue to “flex” the rules.
It came as:
Policing minister Kit Malthouse admitted it was legal to get a take-away coffee as part of your exercise
Cressida Dick backed Boris Johnson for taking a bike ride seven miles from home - but called on Government to define what "local" was
Boris Johnson and top Tories urged “exercise, not socialise” as the Government launched a shock and awe campaign to scare people into staying home.
The PM said as he visited a vaccination centre in the South West yesterday: "We are going to keep the rules under constant review. Where we have to tighten them, we will.
“But we have rules in place which, if properly followed, we believe can make a huge, huge difference."
He urged everyone to stay at home as much as possible to protect the NHS and save lives - and he urged everyone to consider their actions as it was such a "perilous time" for the nation.
Although he stopped short of telling Brits they shouldn't enjoy a take-away coffee in a park, he added: "It’s now that people need to focus - whether they are out shopping, whether they are buying coffee in the park or wherever it happens to be, they need to think about spreading the disease.
"Because as Chris said, one contact that you have can be a chain of transmission for this disease.
"Now is the moment of maximum vigilance, maximum observation and observance of the rules, and of course if we think things are not being properly observed then we may have to do more."
Boris Johnson, seen here at a vaccine centre yesterday, is urging people not to bend lockdown laws
The Health Secretary stressed the bubbles "very important" to make sure people are not left isolate during the lockdown.
But he later said if people continue to abuse rules that say two can meet up outdoors in public to exercise, then that could soon be scrapped.
He told a Downing Street press conference: “Yes, you can go and exercise in the park with one other person, but only one other person.
“And we have been seeing large groups and that is not acceptable. And you should be two metres apart from the other person.
"If there are too many people breaking this rule then we are going to have to look at it.
"But, I don’t want to do that because, for many people being able to go for a walk with a friend, that often is their only social contact.”
WEAR A MASK
Policing minister Kit Malthouse has said that all supermarkets should follow in Morrisons' footsteps to enforce the wearing of masks in stores.
When asked why he thought supermarkets have not done it so far, he told Times Radio: "I think that, understandably, following the November lockdown there was an element of release and therefore the person at the door, the sanitation station, the traffic light system, the queues outside obviously receded a bit.
"What we hope now, and I know all of them will, that they'll see their responsibility and start to put those things back in place."
When asked whether police should intervene, he said some officers have issued fines in retail settings, adding: "What we hope is the vast majority of people, or everybody, will be encouraged to do so by the shop owner."
Matt Hancock ruled out ditching support bubbles
What further restrictions could come in to stop Covid cases rising further?
Ban on meeting other households completely - Matt Hancock said yesterday that if people abused the rule which allowed two people to meet for exercise, the Government would have to look at it again
Cancelling support bubbles - the Government have said they won't do this
A ban on click and collect services - this was reportedly discussed at a Covid O meeting at the weekend
Scrapping takeaways or forcing them to do delivery only - reportedly an option being considered by Nicola Sturgeon today in Scotland
Closing all schools and nurseries completely - this is unlikely to happen
A curfew - some other countries have a strict curfew to force people to return home
Cancelling house viewings - Sir Keir Starmer has called for this, which was banned in the first lockdown
Churches, mosques and synagogues could be closed - Places of worship are currently open for individual prayer and public worship
More face mask rules - SAGE have called for them to be considered in offices and public spaces
The climbdown came after the PM was accused of stretching the rules by going for a weekend bike ride seven miles from Downing Street.
But No10 stressed it was within the rules - and there was no definition of precisely what was "local".
Pressed on the restrictions, Mr Hancock said: “You should stay local, you should not go from one side of a country to another, potentially taking the virus with you.”
Brits have been told only to leave their home to exercise, get food or a small list of other reasons as part of the national lockdown to save lives and cut the number of Covid cases down.
All supermarkets should ban people from coming in without face mask, minister says
It is "preposterous" that anyone could be unaware of the need to follow the coronavirus lockdown rules, the UK's most senior police officer has said.
Metropolitan Police commissioner Dame Cressida Dick wrote in the Times that Londoners have been hosting raves, house parties and gambling events.
The policing minister confirmed Dame Cressida's pledge that rule-breakers are "increasingly likely" to be fined.
Kit Malthouse said people have a "duty" to make this lockdown "the last one".
"We are urging the small minority of people who aren't taking this seriously to do so now, and [are illustrating] to them that if they don't they are much more likely to get fined by the police," Mr Malthouse told BBC Breakfast.
"These current measures should in theory, if we all stick by them, be enough to drive the numbers down so that we can start to move through the gears of tiers from mid-February," he added.
Asked if tighter restrictions were on the way - something the health secretary has refused to rule out - Mr Malthouse said ministers were "on tenterhooks" watching the daily figures for Covid deaths, new cases and hospital admissions, as rules continue to be kept under review.
He said the government's ramped-up efforts to give vulnerable people the coronavirus vaccine should help the UK to "get back to some sort of normality later this year".
The Scottish government's cabinet is due to meet on Tuesday to discuss restrictions.
'Flagrantly ignoring rules'
The latest figures on Monday showed a further 529 people had died within 28 days of a positive test in the UK, while another 46,169 cases were reported.
There are also more than 32,200 people in hospital in the UK with coronavirus, data shows.
Dame Cressida told Radio 4's Today programme some 75 police officers are joining 185 firefighters in being trained to drive ambulances in the capital, as London hospitals struggle with soaring numbers of Covid patients.
In her warning in the Times, she said her officers were still finding people breaking the rules, despite high rates of the virus and clear laws that ban social gatherings.
Reuters
"Most people are doing the right thing to keep each other safe, but sadly a small minority of people continue to flagrantly ignore the rules, for example by holding house parties, meeting in basements to gamble or breaking into railway arches for unlicensed raves," she said.
"It is preposterous to me that anyone could be unaware of our duty to do all we can to stop the spread of the virus," she said, adding that people breaking Covid laws were "increasingly likely to face fines".
In England, Wales and Northern Ireland fines start at £200, but are lower in Scotland. Large parties can be shut down by the police, with fines of up to £10,000.
Dame Cressida said the move towards greater enforcement was "common sense" rather than a show of "dictatorial policing".
Under Scotland's lockdown restrictions, people must start and finish their exercise in the same place - and to do so, they may travel up to five miles from the boundary of their local authority area. People in Wales should start and finish exercising from their home.
Asked if she would like to see similar detail in England's guidance, Dame Cressida said: "That is certainly something the government could consider.
"Anything that brings greater clarity, for officers and the public, in general, will be a good thing."
Police chiefs have been under increasing pressure to enforce the lockdown laws - with a number of news reports about breaches of Covid rules in recent days.
In England and Wales, police have issued 8,000 penalties since November.
In one case, two women were fined £200 each by Derbyshire Police when they drove five miles for a walk together - but the force has since withdrawn the penalties.
After that incident gained widespread media attention, the National Police Chiefs' Council issued fresh guidance to officers.
PA Media
Home Secretary Priti Patel has defended the way police have handled breaches, saying there is a need for "strong enforcement".
But psychologist Prof Stephen Reicher told BBC Newsnight evidence suggested 80-90% of people were by and large obeying the rules - except when it came to self-isolation where compliance was lower.
"The problem isn't people breaking the rules," said Prof Reicher, who sits on a committee of behavioural scientists that advises the Scientific Advisory Group for Emergencies (Sage).
"In many cases it's either the rules aren't clear enough, or the rules are too soft, or else people don't have the support to do what they're asked to do."
England is currently under a national lockdown, meaning people must stay at home and can go out only for limited reasons such as food shopping, exercise, or work if they cannot do so from home.
Similar lockdown measures are in place across much of Scotland, Wales and Northern Ireland - which are in charge of making their own coronavirus restrictions.
So far 2.3 million people in the UK have had a first dose of the coronavirus vaccine, as part of the government's plan to vaccinate tens of millions of people by the spring.
In her article, Dame Cressida said she was "delighted to hear" that a proposal to prioritise frontline officers to get vaccinated was being "actively discussed", as the rate of officers self-isolating has risen.
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