The Metropolitan Police has been asked by the Cabinet Office to confirm it won't publish the 300 photographs its been studying as part of the partygate investigation, a document leaked to ITV News has revealed.
It also revealed the 50 people sent police questionnaires, as part of the partygate investigation, have been warned not to confer with anyone else involved because it could be a separate offence.
The document - an update on the police inquiry into 12 alleged law-breaking parties on government premises during the pandemic - was sent to civil servants by the Liaison Unit - a group set up to support officials through the investigation process.
It said: "The Met has said it has been handed more than 300 photographs as part of its investigation. Consistent with its indication that it will not publish the identities of anyone issued a FPN, we would not expect the Met to publish photographs. The Liaison Unit has asked the Met to confirm this."
Officers began contacting individuals involved in partygate last week, the Met has told the Cabinet Office, and "they will continue to contact individuals this coming week".
It means, as ITV News Political Editor Robert Peston reported on Tuesday, the investigation could still have weeks to run before it concludes.
Downing Street would not say if Mr Johnson had filled in his questionnaire when asked on Monday, but said it would be submitted to police within the seven day deadline, which ends on Friday this week.
Peston also revealed Prime Minister Johnson is paying for a private lawyer out of his own pocket.
Scotland Yard says the questionnaires ask for an "account and explanation of the recipient's participation in an event" and have "formal legal status and must be answered truthfully".
While Number 10 says his questionnaire answers will not be revealed, sources have told Peston the PM's defence will be that he always returned to work after attending any event, meaning his participation was simply part of his working day.
But, if he cannot prove it and police do not think he has a reasonable excuse, it is understood he would be fined.
The leaked document says: "The Met have confirmed that if officers believe it is appropriate, because the Covid regulations have been breached without reasonable excuse, an FPN [Fixed Penalty Notice] would normally be issued."
The Met has confirmed that in line with policy it would not reveal the people who are issued with FPNs, however Number 10 has said it would be made public if the prime minister is fined.
Fines start at £100 for the first offence, growing to £200 for the second offence before doubling for each repeat offence before hitting the cap of £6,400.
Any individual is entitled to appeal their fine, which could see the appellant appear in court.
The prime minister told broadcasters on Monday he would have "a lot more to say" on the allegations against him after police conclude their investigation.
Fifteen Tory MPs have publicly called for Mr Johnson to quit, while more are thought to have privately written to the 1922 Committee of backbench Tories calling for a no-confidence vote.
If 54 submit letters of no confidence there will be a vote on Mr Johnson's leadership which would result in a new leadership contest if he loses and if he wins he'll have another year in office before MPs can try to remove him again.
The PM has been addressing the Ukraine crisis the past few days, attempting to avert a Russian invasion - an issue which he'll be glad has taken the focus away from partygate, even if only temporarily.