Boris Johnson was in his Downing Street flat the night of 'Abba party' being investigated by police

Boris Johnson was in the Downing Street flat the night of a gathering being investigated by police for potential Covid law breaches, The Telegraph can reveal.

The Prime Minister was seen heading up to his flat on Nov 13 2020 - the day Dominic Cummings, his former senior adviser, was forced out of Downing Street.

Abba songs including The Winner Takes It All were heard blaring from the flat, the Mail on Sunday has reported. Mr Johnson has denied there was a party.

On Tuesday, the Prime Minister declined to say whether he was in the flat that night. Carrie Johnson, the Prime Minister's wife, was reportedly there that evening.

On Tuesday, Mr Cummings claimed there were photographs of the Downing Street flat gathering. He called it a “party” and said music could be heard by others in the building.

During a question and answer session online, Mr Cummings - now an arch critic of Mr Johnson - claimed the Prime Minister was not telling the truth, an allegation rejected by Number 10 in the past.

The details emerged after Sue Gray, the civil servant investigating “partygate” claims, published an “update” which revealed the flat gathering is being looked at by the police.

Three of the dozen events which Ms Gray said were being looked at by the Metropolitan Police had not been fully reported on in public when she revealed her findings on Tuesday.

But The Telegraph can reveal that a senior British diplomat in America, a military commander and a senior culture department official are at the heart of the gatherings.

The first of the three newly-documented events happened on June 18 2020 in the Cabinet Office and involved “the departure of a No 10 private secretary”, according to Ms Gray’s report.

The Telegraph understands the official in question is Hannah Young, who left Downing Street to take up the role of deputy consul general in New York.

It is understood about 20 people attended. Alcohol, including wine, was drunk. One government source claimed the event was “raucous”, but another rejected that description.

At the time, social gatherings indoors were forbidden under lockdown laws. A relaxation of the regulations permitted gatherings of up to six people to take place outside.

Martin Reynolds, Mr Johnson’s principal private secretary, is understood to have attended. He is already in the spotlight for organising a “bring your own booze” Downing Street garden event.

It is understood that earlier in the month, Mr Reynolds contacted senior advisers in No 10 to ask their advice on holding a leaving drinks for Ms Young.

A number of people who have served in No 10 are understood to have been questioned by Ms Gray’s investigation team about the leaving do.

The second event was held on December 17 2020 and was described in Ms Gray’s report as “a gathering in No 10 Downing Street on the departure of a No 10 official”.

The Telegraph understands the official who was leaving was Captain Steve Higham, then one of Mr Johnson's private secretaries who advised on defence and national security issues.

Mr Johnson attended the event and gave a speech. The Mirror, which first reported the event before the police investigation began, said Mr Johnson was only there “for a few minutes”.

Tier three restrictions had been implemented the day before in London, meaning people were not allowed to mix indoors with anyone outside their household or support bubble.

Capt Higham is said to have had a close personal relationship with Mr Johnson, who took part in interviews to select the military adviser’s replacement. Capt Higham became Commanding Officer of the HMS Prince of Wales in July 2021.

The third newly-emerged event took place on January 14 2021, described by Ms Gray as “a gathering in No 10 Downing Street on the departure of two No 10 private secretaries”.

The Telegraph understands a senior civil servant in the culture department, who took up the role after leaving Downing Street, was one of the two officials. The other’s identity is not known.

Mr Johnson is also understood to have attended the leaving event. It means the publicly known list of gatherings the Prime Minister was at which are being looked into for Covid lockdown breaches has grown again.

At the time, the UK had just been plunged back into a third lockdown, with people prohibited from holding parties or mixing indoors with people outside of their household.

Ms Young and Capt Higham were approached for comment via spokesmen at the government bodies where they work. No comments were issued.

Downing Street, the Cabinet Office, the Metropolitan Police and government bodies where the three individuals work all declined to comment.

A Foreign Office spokesman said: “It would not be appropriate to comment while a Met Police investigation is ongoing.”