She finally saw a GP, who ordered three consecutive blood tests but drew no conclusions. Frostrup’s diagnosis only came when she saw a female gynaecologist three years later, who broke the news to her that at 50, menopause was well under way, and it was time to consider hormone replacement therapy (HRT).

This was important not least as Frostrup was already showing signs of osteopenia, a precursor to the bone disease osteoporosis. After experimenting with oestrogen patches, she settled on a combination of oestrogen gel and progesterone tablets, which still works for her and she intends to stay on it for life. “Not all women are profoundly affected by symptoms of menopause, but many are and there is still so much misinformation around, especially on HRT,” notes Frostrup.

She has in mind, in particular, the 2002 Million Women Study, which warned of a possible link between HRT and breast cancer, a study she says has since been disproved.

“I wonder if there is even a case for a class action,” she ponders. “Hundreds of thousands of women were put off taking HRT by that study, a drug which would have protected them against heart disease and osteoporosis.”

But that one study is not the only problem. “Most practitioners have little training of menopause – diagnosing or treating it,” continues Frostrup. “But then they have historically shown little regard for tackling women’s health concerns as an independent sector.”

She is also alarmed at recent suggestions that data should be gathered on the grounds of gender, not sex. “It’s imperative we collect by sex. We don’t know what diseases and conditions should be evaluated differently for women,” she says. “It wasn’t until 1996 that women were included in medical trials as separate entities. This has had a major impact on how medicine has served women and it is deeply frustrating.”

Frostrup has been moved by the response of women who watched the documentary or read the book. “I have had floods of strangers coming to me everywhere I went – on a bus, in a bookshop – sidling up to me and saying, sotto voce, ‘thank you’.”

Perhaps her empathy springs from the same place as her imposter-ship? “I know what it feels like to spend your entire working life feeling inferior, especially to those with degrees,” she admits. “I am an autodidact. I am the woman books made.”

Born in Oslo to a Norwegian journalist father and a Scottish mother, Frostrup and her two younger siblings moved to Ireland when she was small. Her parents’ relationship broke down and her father moved to Dublin.

A violent stepfather replaced him, half-siblings arrived, and Frostrup found herself supporting four younger siblings to a large extent. Unable to cope, Frostrup moved out at 13, ending her formal education, and in with her father – and his addiction to alcohol.

He died when she was 15. Eight months later, Frostrup left for London for home life in a squat, starting her career by working for a record company. The next two decades seemed shiny as anything on the outside – parties, fashion, celebrities – and Frostrup was careful not to put a foot wrong. “I’ve had to push and push and push,” she says. “Doors weren’t flying open for me.”

She recalls only letting totally loose on one occasion. “It’s the only time I can remember I was ashamed of,” she says. “It was the wild nights of the Groucho Club era and loads of us had gone back to The Sanderson hotel in St Martins Lane; Chris Evans had taken a suite. Unusually for me, I drank too much, and the room started to spin.

“I stepped outside and vomited on the pavement. I was in my early 30s and it was so unlike me to lose control. I blush now to think of it.”

Her reaction is not that surprising as the daughter of an addict. Like many with dysfunctional families, Frostrup can identify a “hole or absence” inside which needs filling – some use food, alcohol or drugs; for her, however, it was a series of poor relationships in her 20s and 30s.

“I found partners who in some way reminded me of my dad, so that I could try to fix them,” she explains. “That thing I had failed to achieve with my father.” She adds: “I used to say I couldn’t find the right partner but actually I was blind to the right partner. It was only when Jason came along that I was able to see something that was good. It wasn’t fear of commitment – I was dying to commit, but I lacked the skills to make a relationship work.”

Motherhood, however, seems to have come naturally. “I’m very involved. I was up at 6.45am making two grumpy monosyllabic teens a three-course breakfast. I thought, ‘when are you going to stop this? Tone it down a bit’,” she says.

She is surprisingly chilled about the looming empty nest. “I might get more done,” she notes, before adding, “hopefully they will come back a lot. For all that I am nostalgic for when they were little, I love the human beings they are becoming.”

Does she hope that they will follow in her footsteps? “No,” comes the fast response. “My career has been marked by fate and luck – there are large parts I would like to fast-forward through. I have been regarded as a celebrity, a partygoer, one of those people who dresses up and goes to premieres. But the work that I am most proud of is being a journalist. It’s just taken this long for me to get a real job.

“At last I’m not pigeonholed. I’m not Books Mariella, not Showbiz Mariella, not Friend of George Clooney Mariella – I am just me.”

Cracking the Menopause by Mariella Frostrup (RRP £20). Buy now for £16.99 at books.telegraph.co.uk or call 0844 871 1514