In her first public comments since leaving Downing Street in 2020, the former aide also described how staff created a “puppy gate” barrier to prevent Mr Johnson leaving his office during his periods of self-isolation.
In an article for Tatler magazine, Ms Watson, who was brought into government by Dominic Cummings after working on the 2016 Vote Leave campaign, said: “My role at No 10 sounds fancy, but a lot of the time I was much closer to being Boris’s nanny.”
Providing an unflattering depiction of her time in No 10, she said that when testing was limited at the onset of the pandemic in 2020 she “generally” took the PM’s temperature to check whether he had Covid symptoms.
“‘It’s that time again, prime minister!’ I’d say. Each time, never willing to miss a good slapstick opportunity, he dutifully feigned bending over,” she wrote.
Ms Watson also claimed she had to frequently scold the prime minister for “making gags such as ‘Kung-Flu’ and ‘Aye! Corona!’” during the pandemic.
She said Mr Johnson was “pinged” a couple of times by the NHS Covid app which at the time forced people to self-isolate for several days after coming into contact with a person who had tested positive for the virus.
The prime minister, she said, “insisted on working from his downstairs office while isolating”, adding: “Very soon, this required setting up chairs as barriers in the doorway, as he couldn’t resist stepping over the threshold into our adjoining room to peer over shoulders at what people were working on (invariably in a pair of someone else’s ready glasses he’d found lying around).
“So the prime ministerial ‘puppy gate’ was created. He’d kneel on the seats, his elbows propped over the top, like a great unruly golden retriever, howling for attention”.
Describing her own sacking from No 10 in November 2020, Ms Watson claimed the prime minister told her in the Cabinet Room she reminded him of Mr Cummings, who had left the government two weeks previously.
“It’s like a marriage has ended, we’ve divided up our things and I’ve kept an ugly old lamp. But every time I look at that lamp, it reminds me of the person I was with. You’re that lamp”.
She added: “As so many in politics know, the end comes sooner or later — generally sooner, if you’re employed by this prime minister (Although I suppose he’s had karma returned with interest recently).”
No 10 has been contacted for comment.