Ann Mitchell, who was part of a Second World War code-breaking team at the country house near Milton Keynes, died on May 11 2020, aged 97, having tested positive for Covid-19.
Her funeral took place on May 20 2020, the day Boris Johnson’s private secretary is alleged to have arranged a lockdown-busting drinks gathering in the garden at No 10.
Her 63-year-old son, Andy Mitchell, said that just five people were able to attend her funeral in the capital.
“We didn’t complain at the time, because we knew that was what the situation was… I expected any moment to be pulled over by the police to say ‘Where are you going? What are you doing?'” Mr Mitchell said.
“(We had) a very quick chat with my family out in the car park afterwards, and then we all went straight home.
“So, no hanging about, no drinks in the garden or anything like that.
“We knew the situation demanded that we couldn’t hang about, we couldn’t socialise, we had to go home.”
But on the same day, according to an ITV report, Martin Reynolds, the Prime Minister’s principal private secretary, sent an email to more than 100 Downing Street employees inviting them to an evening event and asking them to “bring your own booze”.
Such gatherings were forbidden at the time, even outside.
Mr Mitchell said he was “totally gobsmacked” by the news.
“It was done on an organised basis,” he said.
“It wasn’t just a sort of casual ‘Let’s go outside at the end of the day’, but to actually send out an invitation from the Prime Minister’s office to do that, I’m just stunned.”
His mother deciphered German codes at Bletchley Park, having been recruited from university.
Mr Mitchell said she worked “for the national good”, adding: “She not only did her duty and our service, but respected all the strictures that came with it.
“So, when you see the email (from) Downing Street in May after about two months of (a) pandemic, saying you’ve all been working incredibly hard – she did that for two years, without complaining, without thinking ‘Oh, we’ll just go for drinks, to hell with it’.”
The Covid-19 Bereaved Families for Justice group has said if the Prime Minister attended the alleged gathering his position is “untenable” and he has “lost all moral authority to lead the country”.
Members of the group met Mr Johnson last year in the Downing Street garden, where the gathering is said to have taken place, and said he “looked us in the eyes and told us he had ‘done all he could’ to save our loved ones”.
They said he must “come clean to the country in a way that he didn’t with us”.
Group spokesman Lobby Akinnola, who lost his father Femi in April 2020, said: “It’s beyond belief that the Government seems to be suggesting a report is needed to determine whether Boris Johnson was at the event at all.
“He knows. The dozens of people there know. Why does the Prime Minister need someone to tell him whether or not he was at a party?”