“It was a very, very scary experience,” said Ms MacNamara.
“I felt that it wasn’t in any doubt in my mind at that point that we were heading for a total disaster.”
At the time she said she had warned senior officials, including the then-Prime Minister’s chief of staff Dominic Cummings, that “we are going to kill thousands of people”.
Ms MacNamara told the inquiry that there was a “toxic culture” in Downing Street during 2020 which was “macho and heroic”.
Women’s voices became “invisible overnight”, she added.
The inquiry was shown an extract from Ms MacNamara’s witness statement where she recounted that “not only were there numerous examples of women being ignored, excluded, not listened to or talked over”, it was “also clear that the female perspective was being missed in advice and decision-making”.
Giving evidence to the inquiry, Ms MacNamara said: “It was really, really obvious that not only were there hardly any women there, that when they were there, you know, they had to turn their screens off… on the Zoom meeting or they were sitting in the back row or – there just weren’t any women talking.”
It comes after the inquiry on Tuesday heard how Mr Cummings had used the c-word in messages to refer to Ms MacNamara.
The civil servant also told the inquiry that Covid rules were routinely broken in Number 10.
She described that when guidance was followed “to the letter” during one Cabinet meeting “everybody moaned about it and tried to change repeatedly”.
It took seven months, she said, for hand sanitiser to be installed next to a doorway linking Downing Street and the Cabinet Office despite employees having to use a keypad to gain entry.
“I would find it hard to pick one day when the regulations were followed properly inside that building,” said Ms MacNamara.
It was noted that a high number of officials working in Downing Street had become infected with Covid between March and April 2020, including Health Secretary Matt Hancock, the scientist Neil Ferguson, the cabinet secretary Mark Sedwill, and Ms MacNamara herself.
She also described dealing with the “nightmare” scenario of Prime Minister Boris Johnson falling critically ill with Covid, and ending up in intensive care, in April 2020.
She said: “There were times at this period when it felt like working or living in a dystopian nightmare, that just when one terrible thing had happened the next terrible thing was about to happen.”
The civil servant also told the inquiry of her lack of confidence in assurances about pandemic responses given to her by then-Health Secretary Matt Hancock.
She said there was a “pattern of being reassured that something was absolutely fine, and discovering that something was very, very far from fine”.
Asked about ‘Partygate’ incidents, Ms MacNamara said pandemic-era gatherings in Downing Street “should never have happened”.
She said it was a matter of “profound regret” that she had provided a karaoke machine for a leaving do on June 18 2020.
She said she was worried about the “kind of culture” that staff were working in and the need for them to have space to spend time together, but added: “My profound regret is for the damage that’s been caused to so many people because of it, as well as just the mortifying experience of seeing what that looks like and how rightly offended everybody is in retrospect.”