Police launched a criminal investigation into the ‘partygate’ allegations in January and have been looking at gatherings on eight separate dates between 20 May 2020 and 16 April 2021.

The Telegraph previously revealed how at the event on the eve of the Duke of Edinburgh’s funeral a group of Downing Street employees partied in the basement of No 10 to music played from a laptop, while one staffer was allegedly sent to a nearby Co-Op with a suitcase to fill with wine.

At the leaving party for James Slack, Boris Johnson’s departing director of communications, officials drank prosecco and watched a video farewell message from Theresa May, who was his first boss in Downing Street.

The two events then merged into one, with guests spilling out in the Downing Street garden where one of the partygoers broke Mr Johnson’s young son’s swing.

Dancing and drinking continued into the early hours of the morning on the day the Queen mourned her husband, at a special socially distanced ceremony in Windsor.

The Telegraph understands that a number of fines have been handed out to attendees of that event.

Who is Helen MacNamara?

Ms MacNamara spent two decades in the civil service, rising to become deputy cabinet secretary – one of the most powerful roles in Whitehall.

A Cambridge graduate from a large Irish family, she began her career as an entrepreneur in the dot.com boom of the late 1990s.

But by her own admission her lack of interest in making money proved something of a hindrance in the cut-throat tech industry.

In 2002, amid a civil service drive to recruit more high fliers from the private sector, she joined the Department for Culture, Media and Sport, working for Tessa Jowell.

She worked on London’s Olympic bid and in 2010 was responsible for setting up the Leveson Inquiry into media ethics.

Respected by politicians and ministers on all sides of the house, she joined the Cabinet Office in 2013, and in 2018 took over from Sue Gray as Director General of the Propriety and Ethics Team (PETT).

The role required her to keep ministers and senior civil servants on the straight and narrow and “ensure the highest standards of propriety, integrity and governance within government”.