Show People: The discreet charm of the late-night inquisitor: Kirsty Wark

IT'S 10.45pm, Friday 4 February, and Michael Portillo is having a hard time. He's trying to explain the 'off-the-cuff' remarks he made that day about foreign business ethics. But the television presenter is having none of it. 'A slip of the tongue,' explains Portillo. 'But why did you say it?' asks the presenter firmly. More explanation. More questioning. It could happen to anyone, he says. 'A Cabinet minister]' exclaims the presenter, jabbing the air with her finger. The interview ends in stalemate, but Portillo will remember his encounter with Kirsty Wark, Newsnight's newest presenter.

Wark joined Newsnight in October last year, and presents the flagship current affairs programme once or twice a week, depending on the rota. Her appointment means that, at 39, the former presenter of Breakfast Time, The Late Show, Edinburgh Nights and BBC Scotland programmes too numerous to list, has been elevated to one of the plum jobs in British journalism - the kind of job that makes the news itself.

It's a job to which she seems ideally suited. Sensible, without being boring or middle-aged (I was surprised to discover she's more than 33), Wark has developed an interview style which is confident, unflirtatious but not overtly hostile - a nice contrast with the Paxman hauteur. The obvious comparison is with Francine Stock, her Newsnight predecessor, who had a winning style but often seemed flustered. No chance of that with Wark. The voice is gentle, firm and clear, a doctor's voice - my colleague Jack Hughes once called it the voice of a female John Smith, and that seems about right. So, a good choice on the part of the BBC. But how did she get here? And how on earth does she get home?

Wark commutes to the Newsnight studio each week from the home she shares in Glasgow with her husband, the producer Alan Clements, and two children, Caitlin (aged three) and James (two). Typically, she'll fly south on the morning of a show; and, if it's a Friday, catch the night sleeper home afterwards ('In fact it's a doddle. I rush out of the Newsnight studio, and can be on the train at Euston with a hot chocolate and a brandy before we set off'). The rest of the week is devoted to her family and the production company, Wark Clements, she runs with her husband. A busy schedule, but worth it, she reckons, for the quality of life north of the border ('I certainly wouldn't want to bring up kids in London - so grimy').

Her own childhood was spent in Kilmarnock, where her father was a lawyer - 'Still is at 70]' Kilmarnock in those days was 'a thriving west of Scotland country-industrial town. Of course, since then, one by one the big industries have been slapped down.' Wark attended the quaintly named Wellington School for Young Ladies - 'more like St Trinian's'. A prosperous background? 'In world terms, yes. In fact it was a typical middle-class upbringing'. She read Scottish Studies at Edinburgh University, then found a place among the BBC's graduate entry of 1976.

Production jobs for BBC Radio Scotland and The World at One led to television opportunities - and thence to the other side of the cameras. It sounds like a classic 'discovery', the way she tells it. 'We were doing mock interviews. I was asked to do one. It was just something you were asked to do. Then one of my colleagues said, 'You should try your hand at presenting.' ' A colleague? 'Yes, another producer.' So it wasn't the head of BBC Scotland then? 'Oh no sorry, it was. It was the Head of News and Current Affairs.'

And the rest is history, or more accurately, current affairs. Her first job as a presenter was on Seven Days, a 'bi-media' show - ie on radio and TV at the same time - for BBC Scotland. The CV then reads: Left, Right and Centre ('a straight political programme'); Breakfast Time, her first network job, co-presenter: J Paxman; three years as a presenter (some would say the only bearable presenter) of The Late Show; three as the BBC's woman at the Edinburgh Festival; the heritage series One Foot in the Past (new series in June - you read it here first]); and a host of things for BBC Scotland.

Prior to Newsnight, however, her biggest moment was in April 1990. Mrs Thatcher was to visit Scotland. BBC Scotland had put in for an interview, which was granted. Then Downing Street heard that the interviewer was to be a woman 'and tried to put the kibosh on it'. The BBC stuck to its guns, Downing Street capitulated, and the interview finally went ahead with Wark in the chair. How was it? 'Well, very businesslike. But afterwards she berated me for interrupting her. She said, 'I don't know why you're asking me about the Community Charge time and again - it's here to stay.' And that was in April 1990, you know?'

Thatcher aside, Wark says her sex has not proved a hindrance to her career - something her steady upwards progress seems to confirm. And so to Newsnight.

One way to gauge the programme's influence is to study the Guardian's 'My Media' column. Each week opinion-formers are asked, among other things, which TV programmes they watch. Newsnight's name crops up more often than any other. Last week, Gerry Adams added his name to the list of influential viewers. Even Simon Bates watches. Newsnight may not get TV's largest audience - the BBC claims around a million - but what an audience.

Wark sees her role as 'trying to make sense of the day's news. My job is to ask the questions people want to hear asked, and not to give up after the first answer. It's not any kind of big fancy business.'

Does she ever get nervous? 'Well, I've been doing political interviewing for a long time.' Water off a duck's back, then? 'No, no, if it was you'd do a crappy job. And I don't like all the chumminess that goes on in political interviews. So it's not nervousness, it's adrenalin. I'm not nervous about my interviewees, but I am nervous about doing the job properly. I do think that if you're not being firm and you're not being, you know, persistent, then you're not doing the job properly.'

'Newsnight' is on BBC 2 at 10.30pm, Mon to Fri.

(Photograph omitted)