TALKING to the TV presenter Sarah Dunant is like speaking to her on television when you’re at home. She protects herself from questions with a glass screen, runs the show and you have the feeling that your only control is to switch her off.

The big difference is that in life she’s smaller than on television. Indeed, this self-dubbed Alan Ladd of arts programmes quips that she’s often shot standing on a box. The other difference is that when you talk to her with a cup of coffee rather than an autocue, she doesn’t wear her screen-sized strawberry-frame spectacles.

Dunant, former Kaleidoscope producer and sometime presenter of Woman’s Hour, is a presenter of the cultural magazine programme The Late Show. This week she publishes her third thriller, Fatlands. It is a snappy, Chandleresque novel which charts the further progress of Hannah Wolfe, her independent, feminist private detective from Birth Marks.

The book will be serialised on Woman’s Hour. ‘I read the last one, but didn’t do it well enough,’ says Dunant. ‘I couldn’t get a babysitter so my child was in the studio eating meringue. At the end of episode nine you can hear the crunching.’

Dunant, 42, has curly brown hair, a pinched face and talks with her hands and broadcasterly emphasis. (‘It’s quite clear,’ she says, ‘that I’m not a sex symbol and My Face is Not My Fortune.’) She wears Designer Oxfam – gold day shoes with thick black tights – like her heroine; and she lives in Tufnell Park, like her heroine. We’re talking in her garden, where organic frisee lettuces and cauliflowers grow. Her heroine, on the other hand, only dreams of an alternative lifestyle.

So how many men has she slept with? Eighteen? And mostly SLBA? (Sexual Liberation Before Aids.) That’s a question her heroine gets asked – and answers. ‘You’ll have to ask Hannah.’ Dunant dodges the question. ‘She’s a character. She ain’t me.’

But are there parallels between a female private detective and a television presenter? She laughs. ‘They both get scared. I still get frightened when the green light goes on before big discussions that I’ll let people get away with things and won’t ask the tougher questions because I won’t think quickly enough.’ Is that because she’s not clever enough? ‘No. Thinking on your feet is a different kind of intelligence.’

Dunant is dubbed bossy, brainy, the new Joan Bakewell, the thinking man’s crumpet. She is compared to Cliff Richard and called Brains, after the Thunderbirds character. ‘In the supermarket I’m never mistaken for Cliff. Cliff, however, is always being approached . . .’

She has an acerbic wit but is not a warm personality and comes across as tough, slightly arch and self-satisfied. ‘Occasionally I get over-confident and have a loss of perspective and humility,’ she admits.

She used to drop out. Post-Cambridge University she went to Japan and worked as a hostess in a nightclub. ‘It was severely innocent. But it’s not very nice to sell your company.’

In 1978 she left Kaleidoscope and went to Bogota where she got involved in a drug trafficking network. ‘I met and hung out with a lot of people who were in the cocaine trade. It was the time before the Mafia and Columbian cartels moved in, when there were a lot of independent American operators.’ Did she take drugs? ‘We all did, though many of my generation wouldn’t admit it now. I’ve had very happy times on drugs. I don’t mean ‘happy’ as in ‘out of my skull’, but interesting, creative times.’ She says she wouldn’t take dope nowadays. ‘It doesn’t fit into my lifestyle any more.’ The last time she dropped out was when she went to India, aged 31. A colleague says she was a driven personality when she went, but returned transformed. Was it a life-changing experience? ‘I’ve now been there seven times, including with my kids,’ she replies. ‘But I didn’t turn into John Lennon.’

She gained a sense of perspective. ‘This, the centre of the universe, felt like a very small part. Things other than money are important there . . . But I’ve had more penetrating existential discussions with my five-year-old about God than I’ve had time to have with myself over the last decade.’

Dunant has lived with her ‘partner’, Ian Willcox, for 10 years. ‘I refuse to talk about my private life.’ Why did they never marry? ‘No reason to. It’s never been an issue.’ Willcox runs an independent radio production company. Do they compete professionally or otherwise? ‘No, we do different things. He’s one of those rare men who gets tremendous satisfaction from the home, children and cooking.’ Willcox does the cooking.

Dunant is earnest about women’s issues. She has, to her chagrin, been called a trendy feminist. ‘That’s a lazy insult. It presupposes opportunism and that you only feel those things because everybody else does.’ She is a committed feminist who fights for equality between the sexes in all areas, particularly since Zoe (five) and Georgia (two) were born. ‘I keep wondering whether because they’re little girls some things will be closed to them.’