Another of the gatherings for which attendees are likely to face fines is the “bring your own booze” party held in the Downing Street garden on May 20. 2020, which Mr Johnson claimed he had believed was a work event.

Those unable to provide a “reasonable excuse” for attending one of the illegal parties will be issued with fines. The amount people will be fined will depend on their role and when the event was held, but anyone deemed to have organised an event could potentially  face a fixed penalty notice of up to £10,000.

If people do not reply to the questionnaires, or their explanation is not accepted, police will contact the ACRO Criminal Records Office who will confirm the decision to issue the fine and will send notice by post.

A Scotland Yard spokesman said: “Detectives working for the Met’s Special Enquiry Team continue to examine more than 500 documents and 300 images provided to them by the Cabinet Office, and will be requesting further information from the Cabinet Office to assist with the investigation.

“There may be also be a need to contact further people in the coming days and weeks, should they be identified as having taken part in an event and having potentially breached regulations. It should be noted that being contacted does not mean a fixed penalty notice will necessarily be issued to that person.

“Nevertheless, if following an investigation, officers believe it is appropriate because the Covid regulations have been breached without a reasonable excuse, a fixed penalty notice will normally be issued.

“We understand the interest in and impact of this case, and are progressing the investigation at pace. We are committed to completing our investigations proportionately, fairly and impartially.”