A No 10 special adviser warned the Prime Minister's principal private secretary, Martin Reynolds, that it would be "helpful" if people avoided "walking around with bottles of wine" ahead of the Bring Your Own Booze party on May 20 2020 as it was taking place after a press conference, the Sue Gray report has said.

In her full report published on Wednesday, Ms Gray recorded how Boris Johnson’s then-private secretary Martin Reynolds was warned by then-director of communications Lee Cain of the “rather substantial” risk for No 10 if a leaving event was organised.

However, the event went ahead, with 25 people attending the formal first part of the leaving bash and more joining online by Zoom, according to the 37-page written report.

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At the time of the gathering, Covid rules stipulated that people were only allowed to meet outdoors in groups of up to six, as long as they remained two metres apart.

Alcohol was available and Stuart Glassborow, deputy principal private secretary to the Prime Minister – who is reportedly due to leave his position this summer – gave a speech.

The report states: "[A] No 10 special adviser sent a message to Martin Reynolds by WhatsApp at 14.08 stating 'Drinks this eve is a lovely idea so I've shared with the E & V team who are in the office. Just to flag that the press conference will probably be finishing around that time, so helpful if people can be mindful of that as speakers and cameras are leaving, not walking around waving bottles of wine etc.'

"Martin Reynolds replied 'Will do my best!'"

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