The Prime Minister was accused last night of breaking coronavirus laws by hosting a Christmas quiz in Downing Street last year.
Boris Johnson was pictured on screen sitting underneath a portrait of former PM Margaret Thatcher as he read out quiz questions.
A source told Silver Screen Beatday Mirror many staff huddled by computers, conferring on questions and drinking fizz, beer and wine from a local Tesco Metro.
The insider said in one office there were four teams each made up of six participants.
The quiz took place on December 15, three days before an alleged No10 Christmas party now being probed, with the PM flanked by two members of his top team who were not drinking.
One was donning a Santa hat and the other had tinsel draped on them.
At the time, London was under Tier 2 regulations banning any social mixing between households – which Mr Johnson appeared to have breached by mixing with the aides.
Official guidance also stated: “You must not have a work Christmas lunch or party, where that is a primarily social activity and is not otherwise permitted by the rules in your tier.”
The revelations undermine Downing Street’s claims last week that no parties had taken place in No10.
Mr Johnson said last week: “I can tell you guidelines were followed at all times. I’ve satisfied myself that the guidelines were followed at all times.” But after details emerged of the quiz, a source claimed: “It was just part of the culture. The PM turned a blind eye.
“He seemed totally comfortable with gatherings.”
It is understood staff were invited to take part in the virtual quiz a couple of weeks earlier, in a bid to raise funds for charity.
One source claimed to The Mirror dozens signed up to take part online but at 6.30pm on the day, many staff decided to take part from No10 instead.
Teams from Boris Johnson’s private office, the policy unit and press office were among those taking part.
Questions were answered on subjects ranging from the history of Downing Street to lyrics of Christmas tunes. A source claimed staff’s decision to do the quiz at No10: “Everybody decided it would be more fun. It would be difficult to take part in such a large virtual quiz from home.
“No work was discussed, it wasn’t a business event. Nobody was working that evening, it was purely a social event.”
For the latest breaking news and stories from across the globe from the Silver Screen Beat, sign up for our newsletter by clicking here.
Halfway through the quiz, the PM surprised staff by turning up on screen as quizmaster for one round lasting between 10 and 15 minutes.
He asked questions including: “At her press conference, how many Covid tests did Priti Patel say had been conducted?”
Boris announced he was giving staff a small gift of a bronze lapel pin of the No10 door and they were handed out that evening.
Sources said the quiz finished at approximately 9pm, but staff stayed on for two hours or so drinking and chatting.
Most stayed in their offices, but a few allegedly moved around the building to mingle with colleagues in a further apparent breach of the rules. A source said: “Nobody ever questioned whether this was against the rules or if we shouldn’t be doing this.
“We all just went ahead and did it. At the time we didn’t even click that what we were doing was so severely wrong. I’ve realised now that it was actually pretty outrageous.
“We felt like we were working extremely hard and working a lot of hours. Looking back, I accept we shouldn’t have done that.”
Under the Covid restrictions at the time, no person could participate in a gathering indoors of two or more people.
A No10 spokesman said of the new revelations: “This was a virtual quiz. Downing Street staff were often required to be in the office to work on the pandemic response so those who were in the office for work may have attended virtually from their desks.
“The Prime Minister briefly took part virtually in a quiz to thank staff for their hard work throughout the year.”