Neither A-level nor GCSE students were able to sit public exams this year because of the coronavirus pandemic.
Thursday's A-level results saw almost 40% of all grades marked down from teachers' predictions.
Ofqual confirmed appeals using mock results could begin from Monday and would apply for GCSE, AS and A-level students as well as those taking Extended Project Qualifications and Advanced Extension Award in maths.
The government had already announced any school could query a final grade if it was a lower that a student's mock exam.
But with schools shutting down in March, there was a lack of clarity over what constituted a mock exam with some students complaining they did not get a chance to sit one.
'Face-saving exercise'
Ofqual says it will allow a "non-exam assessment mark" as the grounds for an appeal.
Geoff Barton, general secretary of the Association of School and College Leaders, criticised the process, branding it "surreal and bureaucratic".
He said: "This is clearly a face-saving exercise by a government which has said that it won't do a U-turn on its pledge that moderated grades will stand, come what may.
"Instead, it is attempting to remedy the grading fiasco through an appeals process so surreal and bureaucratic that it would be better off at this point doing that U-turn and allowing original teacher-assessed grades, where they are higher, to replace moderated grades."
He added: "We don't blame Ofqual for the bizarre nature of the appeals criteria. The regulator has been given a hospital pass by a Government that is in disarray. It is time for ministers to stop the chaos and fall back on teacher-assessed grades rather than prolong this nightmare."
Flypasts by the Red Arrows and vintage Second World War aircraft have been part of poignant commemorations to honour those who fought in Far East.
Tributes to veterans and those who lost their lives have been led by Prince Charles on the 75th anniversary of VJ Day, saying they should be "respected, thanked and cherished".
And a two-minute silence was held, marked by the sounding of the Last Post at the National Memorial Arboretum in Staffordshire.
Image:A Lancaster bomber, three Spitfires and a Hurricane perform a fly-past over the National Memorial Aroboretum on the 75th anniversary of VJ Day
Image:The Red Arrows fly over Belfast - but their appearance over Edinburgh, Cardiff and London was called off because of bad weather
Although VE Day (Victory in Europe Day) arrived just over three months earlier, it was not until 15 August 1945 that the Second World War finally came to an end with the surrender of Japan.
Charles, who laid wreaths with the Duchess of Cornwall at the arboretum, said those who fought in the Far East had been labelled "the forgotten army".
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About 40 veterans attended the anniversary VJ Day service.
Richard Day, 93, who was involved in the decisive Battle of Kohima in northeast India, said the worst part was "crossing rivers at night", then going through the small hours in wet clothes with wet equipment.
He said the Japanese were "very determined for their emperor" and "didn't appear to have any fear at all".
Image:Prince Charles lays a wreath at the National Memorial Arboretum
PM: 'We will remember them'
More than 71,000 British and Commonwealth troops died in the Far East campaign, including 13,000 who lost their lives in Japanese prisoner of war camps, where conditions were brutal.
In a speech, the Prince of Wales said many of the "soldiers, nurses and other personnel felt anger and disappointment at how they were treated when they finally returned home from a war which, from the public's point of view, had ended on the 8th May 1945 (VE Day)".
He added: "Let us affirm, they and serving veterans are not forgotten, rather you are respected, thanked and cherished with all our hearts and for all time."
Image:The Prince of Wales helps 97-year-old veteran Darbara Singh Bhullar lay a wreath
Image:The Duchess of Cornwall chatted with veterans following the service
Boris Johnson read the Exhortation before a two-minute silence, which was followed by a Battle of Britain Memorial Flight flypast, involving three Spitfires, a Hurricane and a Lancaster bomber.
In a letter to veterans, the prime minister said: "You fought for freedom, brought the Second World War to its end, and restored peace and prosperity to the world. On this anniversary, and every day hereafter, you will be remembered."
In a statement, the Queen mentioned the "joy at the end of the conflict", but also remembered the "terrible devastation that it brought".
The Duke of Edinburgh, 99, served in the Second World War as a naval officer, and will feature alongside other veterans on a number of large screens across the UK, in a photo montage showing veterans today and when they served.
'When we forget, the world gets worse'
Defence Secretary Ben Wallace told Sky News that those who fought were coping with "horrendous conditions" and it was "time to remember what they did".
Mr Wallace added that four million people from the Commonwealth and India contributed to the fight.
He said it was a collective effort involving "different nations, different races and different religions".
Image:Japanese Prime Minister Shinzo Abe spoke during a memorial service in Tokyo
A new audio experience has been released at the Imperial War Museum to commemorate VJ day with the voices of veterans.
The Red Arrows had to cancel a flypast over Edinburgh because of unsuitable conditions. The group's leader, Martin Pert, tweeted that the weather was "particularly challenging".
However, flypasts did go ahead elsewhere, including over Prestwick and Belfast.
Red Arrows flypast for VJ Day
In Japan, Prime Minister Shinzo Abe pledged "never to repeat the tragedy of war" and Emperor Naruhito expressed "deep remorse" over the wartime past.
Veteran Roy Miller, 96, joined the Royal Navy at the age of 15 and served in the gunnery division onboard the aircraft carrier HMS Indomitable in the Far East.
Speaking to Sky News from his Surrey home, he said: "People often ask if I celebrated when it all ended, but it wasn't joy at all. It was relief. It was an end. It was a feeling of relief that the whole thing was coming to an end and we weren't going to be shot at any more."
Thunderstorms, lightning and heavy rain are forecast to hit parts of Britain this weekend, with flooding expected to cause travel chaos.
The Met Office has issued a yellow thunderstorm warning for large areas of England and Wales for the next three days.
The extreme weather may damage buildings and cause power cuts and cancellations to train and bus services, while flooding could cause roads to close.
The South of England and Wales are likely to have the most rainfall, with frequent lightning, gusty winds and heavy downpours with 30 to 40mm of rain possible in less than an hour, according to the Met Office.
Five flood alert warnings have been issued across the West Midlands by the Environment Agency.
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Met Office forecaster Matthew Box said: "Saturday will begin mostly cloudy for most areas across the UK but as the day goes on showers will start to break out in the South and South East of England.
"As the day progresses further there's a chance of some rumbles of thunder and potentially some hail and lightning.
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"The risk of thunder will start to push further north on Sunday, with central parts of England and Wales facing heavy rain and the chance of flooding."
However, areas in Scotland and north-western England and Northern Ireland are forecast to be dry with a few sunny spells after a week of heavy rain.
Mr Box said this was due to winds causing an "East-West" split in northern areas.
Image:Yellow warnings have been issued for parts of England and Wales. Pic: Met Office
Chief Meteorologist Frank Saunders added: "Up until Monday, thunderstorm warnings cover much of England and Wales, with parts of southern England and South Wales seeing the greatest likelihood of impacts."
Due to the continuing hot weather, large parts of the UK will be at risk of thunderstorms, Mr Saunders explained.
Neil Davies, Flood Duty Manager at the Environment Agency, said: "Isolated thunderstorms could bring sudden surface-water and river flooding, which may lead to flooded properties and severe travel disruption in some areas. Further surface water and river flooding is also a possibility until Sunday.
On Monday, northern Scotland is expected to be sunny, while showers are forecast in the East.
Elsewhere, there will be sunny intervals, showers or thunderstorms.
Tuesday will see sunshine and showers, with rainfall particularly heavy in the North, while Wednesday is forecast to be drier in the South with showers further north.
Places could see up to 30mm (1in) in an hour and up to 50mm in three hours on Saturday, with 90mm (3.5in) in some places on Sunday.
Saturday's warning covers Blaenau Gwent, Bridgend, Caerphilly, Cardiff, Merthyr Tydfil, Monmouthshire, Neath Port Talbot, Newport, Rhondda Cynon Taff, Torfaen and Vale of Glamorgan.
The Met Office said Monday's thunderstorms may be accompanied by large hail stones, frequent lightning and gusty winds.
Thunderstorms have brought flash flooding and power cuts to parts of Wales throughout the week, prompted by the spell of hot and humid air across parts of the UK.
The Red Arrows Edinburgh flypass has been cancelled today due to the weather.
It was scheduled to take place at around 11.29am, before heading to Prestwick at 11.39am, as part of the UK-wide event to mark the 75th anniversary of VJ Day.
Many Scots headed out to try to catch a glimpse of the aircrafts flying overhead.
But heavy clouds in the capital have put a stop to the planned flypass.
The Red Arrows have continued to their next stop of Prestwick, where they have made a schedule landing for refuelling.
The Red Arrows flypass in Edinburgh has been cancelled (Image: PA Wire)
We'll be bringing you the very latest updates on this breaking news story.
The iconic Red Arrows will soar over Scotland today to mark the 75th anniversary of VJ Day.
The UK-wide flypast is the first of its kind since the London 2012 Olympic and Paralympic Games.
The red planes are visiting all four capitals as part of celebrations marking the end of World War 2.
The RAF jets will fly over Berwick Upon Tweed at 11.16am before soaring over the sea near Eyemouth three minutes later.
Members of the public in the St Andrews area should turn their heads to the sky at 11.23am before the jets turn around and head to the sea near Longniddry at 11.28am.
The Red Arrows are set to appear in the skies over Edinburgh at 11.29am before travelling to Prestwick, Ayrshire, for refuelling.
The iconic group will then take off from the airport and head south over Dunure at 1.45pm.
The Red Arrows are coming to Scotland
They will fly over Ballantrae at 1.50pm, Cairnryan at 1.51pm and Portpatrick in Dumfries and Galloway at 1.52pm.
The Red Arrows while they fly across to Northern Ireland to continue their tour of the UK.
Japan ceased fighting with the Allied forces on August 15, 1945, three months after Nazi Germany did the same.
Plans to mark VJ Day were scuppered by the pandemic meaning the Red Arrows flypast is the main event taking place on Saturday.
Ahead of the occasion Prime Minister Boris Johnson said: "When the Second World War ended 75 years ago with the surrender of Japan, British soldiers, sailors and airmen were serving in the Far East, fighting hard to achieve victory - and were among the last to come home.
On this anniversary I want to remember what we owe the veterans of the Far East campaign.
“They brought an end to the Second World War, they changed the course of history for the better, liberated South East Asia, and many paid the ultimate sacrifice.
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“That's why on this remarkable anniversary - and every day hereafter - we will remember them.”
Emergency services are at the scene after a train crashed into a vehicle on the tracks in Johnstone shortly after 6am this morning. The driver was rescued from the car by firefighters before being treated by paramedics.
The driver was rescued from the car by firefighters before being treated by paramedics.
The Scottish Fire and Rescue Service dispatched nine crews to the scene and helped the nine uninjured passengers from the train along with Police.
A Police Scotland spokeswoman said: "A report was received around 6.15am on Saturday August 15 that a train had collided with car near Johnstone, Renfrewshire.
"Emergency services are in attendance."
A spokeswoman for the fire service said: "We were alerted at 6.26am on Saturday August 15 to reports of a collision between a car and a train.
"Operations Control mobilised nine appliances in total to Janefield Avenue in Johnstone, Renfrewshire.
"Firefighters removed the driver from the car before transferring them into the care of paramedics.
