Thousands of fans ditched face coverings to roar on England and Scotland at Wembley last night despite stadium rules saying they must be worn.
Pictures show the majority of supporters with masks below their chin or not being worn at all while singing and cheering on their team during the 0-0 Euros clash.
UEFA (the Union of European Football Associations) stipulates on its website that face coverings should be worn over the nose and mouth at all times while attending a match at Wembley - unless medically exempt.
The administrative body also says that masks can be taken off while seated for eating and drinking.
Other Covid restrictions at the stadium include keeping a distance of at least 3.3ft (1m) to other fans, arriving within an allocated 30-minute time slot and avoiding hugs, high fives and any close contact with others.
The images come after raucous clashes in central London last night, which saw 30 people arrested following the tense encounter at Wembley.
Many have questioned why Nicola Sturgeon allowed Scottish fans to travel south as she appealed for them to 'stay safe' on Friday and 'be respectful to our hosts' amid the spread of the Delta variant.
England fans sing the National Anthem during the UEFA Euro 2020 Championship Group D march between England and Scotland at Wembley Stadium last night in London
Scotland fans react in the stands during the match at Wembley Stadium on Friday evening. UEFA (the Union or European Football Associations) stipulates on its website that face coverings should be worn over the nose and mouth at all times
England fans show their support in the stands prior to the match at Wembley Stadium in London. UEFA says that masks can be taken off while seated for eating and drinking
Breakdown of Covid rules for fans at Wembley
As part of its Covid guidance for Euro 2020 matches at the stadium, UEFA states: 'You will need to wear a face covering at all times, unless you are medically exempt.
'Any type of face covering which safely covers mouth and nose is permitted. You can safely take if off while you’re seated to eat or drink.'
It adds: 'If you're exempt from wearing a face covering for medical reasons, you will not need to wear one at the stadium.
'You must be in possession of a doctor's certificate proving your exemption.
'Please be ready to show it upon entry and also to security staff in the stadium as required.'
UEFA also says in its matchday checklist: 'You will need to wear a face covering at all times during the match.
'Any type of (covering mouth and nose) is permitted. You'll need it for travelling on public transport.'
Some have noted the irony that Sturgeon imposed a travel ban to Manchester and Salford because of rising cases there at the same time as tens of thousands of Scots travelled to London without a ticket to the game.
The First Minister strongly condemned the thousands of Rangers fans who gathered earlier this year to celebrate their league title, but has not spoken out strongly against the Scottish supporters descending on London.
Before the end of the match yesterday, police cleared fans out of Leicester Square and sealed off the five entrances to the area, wary of any potential flare-ups between supporters.
Squads of police in fluorescent yellow jackets formed a human barrier to stop any fan from entering, while the William Shakespeare statue - which was scaled throughout the day - was also sealed off.
Scotland's supporters cheer before the start of the UEFA Euro 2020 Group D football match between England and Scotland at Wembley Stadium in London on June 18
Scotland fans show their support following the match last night. As part of its Covid guidance for Euro 2020 matches at the stadium, UEFA states: 'You will need to wear a face covering at all times, unless you are medically exempt'
Scotland fans react after the UEFA match between England and Scotland on June 8. UEFA also says in its matchday checklist: 'You will need to wear a face covering at all times during the match. Any type of (covering mouth and nose) is permitted'
Scotland fans react in the stands after the football match between England and Scotland at Wembley Stadium last night
England fans pose for the camera while inside the stadium before the match. Other Covid restrictions at the stadium include keeping a distance of at least 3.3ft (1m) to other fans and arriving within an allocated 30-minute time slot
One England fan was arrested for taking a swing at an officer after he became angry at being unable to pass a police line. The other arrests included for racial aggravation, drunk and disorderly behaviour, possession of drugs and knuckle dusters.
One man - believed to be a Scotland supporter - had to be rushed to hospital after he fell from a sixth-floor window of a hotel in Lancaster Gate last night. His condition is not believed to be life-threatening, Met Police confirmed.
While Leicester Square was cleared before the match finished, more than 1,000 fans poured back into to the area from pubs in central London later in the night. Police eventually took the decision to allow them back inside the cordon.
Today, workers will have to clean up the mess from the night before, with the area described by some on social media this morning as looking 'like a war zone'.
Thousands of empty beer cans and bottles were left strewn over pavements, along with bags of rubbish and traffic cones lodged in mud thickened by yesterday's torrential rain.
Fans leave Wembley Stadium after the UEFA Euro 2020 Group D match between England and Scotland on Friday, June 18
Fans chanted after the famous result which leaves Scotland with a glimmer of hope of qualification if they win their final group game
One man - believed to be a Scotland supporter - had to be rushed to hospital after he fell from a sixth-floor window of a hotel in Lancaster Gate last night. His condition is not believed to be life-threatening, Met Police (pictured at the scene last night) confirmed
Workers will today have to clean up the mess from the night before, with the area described by some on social media this morning as looking 'like a war zone'
A mass clean-up begins this morning after the Tartan Army left Leicester Square covered in litter for a second consecutive night
A total of 30 people were arrested in central London as part of the policing operation for the Euros clash, Met Police said.
The force added 25 of the arrests were in central London while five people were arrested in the vicinity of Wembley.
Scotland Yard said in a tweet today: '13 arrests were for public order offences, six for drunk and disorderly, four for assault on police, three for assault, two related to Class A drugs and one each for breaching a dispersal order and breaching a banning order.'
Leicester Square fell within a dispersal area giving police powers to move people out. One police officer said last night: 'No fans are being allowed to congregate here for the rest of the night.'
MailOnline has reached out to UEFA and Wembley Stadium for comment.