Met Police cops investigating lockdown-busting parties at Downing Street have begun quizzing key witnesses.
The Partygate probe was launched after reports, first broken by the Mirror, revealed there had been a series of rule-breaking gatherings in No10.
So far, over 100 questionnaires have been sent to people believed to have been at the parties, including Prime Minister Boris Johnson and Chancellor Rishi Sunak.
Scotland Yard detectives leading the probe will now begin interviewing people as part of Operation Hillman.
The PM could be slapped with a fixed penalty notice if he is found to have breached the rules he put in force during the pandemic.
The Met has confirmed it has been handed more than 300 photographs, one of which is said to be an image of the PM with a can of beer in his hand celebrating his birthday in June 2020.
The force is investigating 12 events, including as many as six which Mr Johnson is reported to have attended.
An update by the Met Police today said: "To date, over 100 questionnaires have been sent out asking the recipients about their participation in alleged gatherings.
"The questionnaires provide recipients with the opportunity to give an account of their involvement and the responses form part of the investigative material for the operation. Recipients are given seven days to respond.
"As a result of responses so far, further individuals have been identified and questionnaires sent to them. As the investigation continues, we may need to contact more people as further information comes to light."
The Prime Minister's personal approval ratings have plummeted since the allegations emerged late last year and several Tory MPs called for him to quit.
Senior civil servant Sue Gray has published Whitehall's interim report into the parties, in which she slammed “failures of leadership and judgement” in 10 Downing Street.
Her nine-page update said "at least some" of the gatherings were "a serious failure to observe not just the high standards expected of those working at the heart of Government, but also of the standards expected of the entire British population at the time."
Mr Johnson told MPs he was “sorry for the things we simply didn’t get right”, adding: “I get it and I will fix it.”
Ms Gray is expected to publish all of her findings when the police investigation has concluded.
