Rishi Sunak has been sent a questionnaire by the Metropolitan police over his attendance at a birthday party held for Boris Johnson while tough Covid restrictions were in force. The chancellor has not yet responded but has seven days to do so, and will be able to set out why he was at the gathering in a bid to avoid being fined £100. It comes nearly two weeks after the prime minister received a questionnaire from Scotland Yard as part of its Operation Hillman investigation into a dozen alleged parties that may have fallen foul of rules on social mixing. Sunak is understood to have attended a gathering on 19 June 2020 in the cabinet room, along with the prime minister’s wife, Carrie, the interior designer Lulu Lytle and other Downing Street staff. A cake was presented to Johnson, but ministers have sought to dismiss the significance of the event. One, the Northern Ireland minister Conor Burns, said the prime minister was “ambushed by cake”, while another, the transport secretary, Grant Shapps, said the gathering lasted only 10 minutes. Sources close to Sunak have said he simply happened upon the celebrations, and believed it was inevitable he would receive a questionnaire given that he both works and lives in Downing Street. However, the Mirror reported earlier this month that police had obtained a photograph of Johnson holding a can of beer while standing next to Sunak. Scotland Yard has said that being handed a questionnaire is the equivalent to being interviewed under caution. All recipients of the form are asked what the purpose was of their participation in the event under scrutiny, how long they were there, who else was there and, crucially: “What, if any, lawful exemption applied to the gathering and what reasonable excuse did you have for participating in said gathering?” More than 88 questionnaires have reportedly been sent out so far, with the outgoing Met commissioner, Cressida Dick, suggesting earlier this month that “some – but probably not all – may very well end up with a fixed penalty notice”. The fine it carries is £100, though those who wish to appeal against it will see the issue referred to court. Sunak was asked several weeks ago if he was worried that the string of Downing Street parties had damaged public confidence in the government. He told the BBC: “Yes, I think it has. I can appreciate people’s frustration. And I think it’s now the job of all of us in government, all politicians, to restore people’s trust.”