'People are drawn to the complexity of my games'

Since Prime Suspect first hit the screen, Lynda La Plante has been one of our most successful, if undervalued, TV dramatists. Now, at 57 (or is it 61?), she is also experiencing the joys of motherhood for the first time

There is no Lynda La Plante HQ at the address in Soho I've been given - just a copy shop. Oh dear. Fortunately, the man behind the counter has had a good lunch and volunteers the use of his phone. 'Nah, don't worry about it, love,' he says with a wink. 'Help yourself.' London. Don't you love it?

Lynda La Plante doesn't. Finally traced to a first-floor corner office on the other side of the street, with a lordly wraparound perspective on the tourists and advertising creatives, she has a much bleaker view. People roll their eyes at 'the darkness' in her TV shows, she tells me, in her deep, unhurried, duchessy tones, but 'the darkness is all around us. It's very easy to see. It's down there in the street. We just had a guy screaming abuse, stark naked, trying to knife somebody over there in broad daylight. We've had four rapes in this street. Every single girl in my office has been mugged and burgled - sometimes repeatedly. It is life'.

We live, La Plante assures me, in a very violent world. That's why people watch her tar-dark thrillers. They are a televisual comfort blanket, a fact I had not taken on board while watching the forthcoming Trial and Retribution - Blue Eiderdown (semen stains, bondage dungeons, pathologists saying: 'Now we get to the unsavoury bit'; all in all, a nastier vintage than the competition) through the grid of my fingers. 'People are drawn to the complexity of my games, the cleverness of the solution.' It's all about putting the pieces together, you see, a process unlike the irresolution of real life, where bits of the puzzle get lost under the sofa and you never manage to finish the sky.

Since 1991, when the first Prime Suspect introduced audiences to the concept of event television, a devalued term nowadays, La Plante has been one of the UK's most successful TV dramatists. Yet the industry does not rate her particularly highly. She is viewed as a brand, a franchise, a bit of a cookie-cutter, unlike Paul Abbott, Tony Marchant and Stephen Poliakoff, writers who come at the medium from an predominantly literary tradition rooted in The Wednesday Play and the Royal Court.

'La Plante's house style is to do with the format, not with individual scenes, twists or language,' says one TV screenwriter. 'It's almost as though she's a writer/producer in the American sense.' La Plante's strength is in her formula and she churns out different spins on it year after year. Prime Suspect was about a woman battling to prove herself in the police force, as is The Commander, with Amanda Burton, now in post-production, not forgetting The Governor, in which Janet McTeer battled to prove herself in the prison service. (A predominant theme in Trial and Retribution, set in both a knocking shop and a cop shop, is workplace misogyny.) From her first TV script, Widows (1983), La Plante's stories have centred on strong women struggling in a predominantly male world, a world perhaps not too unlike the industry which views her with a little reservation today.

When asked whether she feels she has been undervalued because she sticks to a format, she agrees without any sign of rancour. She explains that Prime Suspect 'forced the issue of the way I work. It introduced me to the way I will now work forever'. She won't deviate because Prime Suspect 'was my intro to America, my calling card. I am, and will be, eternally grateful for it'. But yes, she finds her treatment galling. 'Totally. I am totally dismissed. My track record gives me no security at all. I have a letter from the BBC saying, "Please send in your treatment and if we like it we may commission it to a script." My name means nothing. I could have sent it in as Warren Bittelbum and got the same reaction. And probably Warren Bittelbum would have been in with a far greater chance than anything I'd written.'

She starts to pick at her Starbucks cup. Since setting up her own company and starting to produce, she has sold several dramas to US networks. In America, they understand her and what she pragmatically refers to as her 'product'. Right now, both Tom Cruise and Harrison Ford are pawing over a recent novel and there's something happening with Barry Levinson that sounds rather hush-hush. 'In America, I'm treated with far more respect. It's quite extraordinary, the difference.'

La Plante may be 61 or 57 (whose account to believe?). She has a bright, ruddy bonfire of hair, expressive eyes heavily hemmed with mascara and fingers that clank with gold and diamonds. She is a trim little creature (she takes her latte skimmed and makes an 'ooh' face when I ask for a fat one) with a string of pearls and a bubblegum-coloured jersey slung around her neck.

She looks and speaks like the character actress she used to be. With lots of eye-rolling, dramatic pauses and irritated laughter, she tells me about a trip to the BBC nine months ago to see Jane Root, then controller of BBC2, and how everyone messed up her name. 'The guy at the front desk asked me three times how to spell it. He kept saying, "It's Linka La Planke."' When she was finally ushered up to the controller's office, after being kept waiting in reception for 45 minutes, Jane Root turned around, held up her hand, and said: 'Give me five minutes.'

La Plante sighs. 'I thought, wonderful. Twenty-five years writing and I get, "Give me five minutes." So I said, "I'm sorry, I don't actually have five minutes now." It would be nice to feel that I was at least being shown respect.' Her Starbucks cup is, by this point, macrame. She chucks it in the bin with a shrug.

If you want a crash course in La Plante's accomplishments as a TV writer/producer, you can do no better than pick up her new novel, forgettably entitled Above Suspicion. It's a routine police procedural thriller, in which a young and ambitious detective finds her feet in a murder investigation. The usual themes crop up: as in Trial and Retribution, there's a honeytrap, workplace discrimination, sex with inappropriate people. The difference is that Above Suspicion is as flat and plain and unshowy as a water biscuit. The sense of menace that penetrates her TV projects is entirely missing. This is her 10th novel. Her sales figures are always decent, but for all sorts of reasons (not least because she's worth something like £25 million), I wonder why she bothers. 'I love it. I can never say that any TV project that I've written is mine, truthfully.'

Does she accept that perhaps she is better at working collaboratively, with input from co-producers, directors, editors and actors, than on her own? Again, she doesn't take umbrage. 'I probably am,' she agrees. 'But a book is me. So when you pick up the book, it's my humour, my twists; no one else has had their hands on it but me and the police advisers. I love that process of unstoppable writing. Oh, it's lovely.'

La Plante is famous for immersing herself in research. In the early days, she did it all herself, talking to victims, lawyers, scientists, detectives. Now, though she still turns up to high-profile court cases (she was in the public gallery at the Jeremy Bamber appeal and the Huntley trial), she has a team of researchers. The relationship she has worked hardest to maintain is the one with the police, who help her with access as well as fact-checking.

'We get on. We work together. I never put anything in my script that isn't passed by them. My scripts have police fingerprints all over them: "Your DNA result is too early"; "The blood spray is going the wrong way." Some people would find that very frustrating but I don't. It always advances the script.' She is a terrific advocate of the police (even though in her screenplays plenty of officers are rather bent).

This interests me because a friend has said that in a film-school lecture many years ago, talking about researching the first Prime Suspect, La Plante remarked that she paid a notorious criminal's wife to facilitate a meeting with her husband and passed herself to the Broadmoor authorities as his sister-in-law. I ask if this is true.

'You can't let that out,' says La Plante. Then she mumbles a bit. Sorry?

'That was very early on,' she says, clearing her throat. 'I would never do that now. That was illegal. I can't ask the police to protect me and then do something like that. The prison authorities gave me open access for The Governor; if they'd known I'd done something like that, they wouldn't have helped me. To have these sessions is, you know, unbelievable. That [story] was told on the condition it was never repeated.' She doesn't deny it and she tells me that, in the early days, to get around the regulations, prisoners' wives 'would have a new fridge, stuff like that. Not a new car, but it would be a domestic thing that would help them, rather than cash'.

Since the themes that she returns to are so specific, it's striking that her own background seems so innocent, so uneventful. La Plante - or Lynda Titchmarsh, as she was then - grew up comfortably in Crosby, Liverpool, the daughter of a sales manager. There was blackberrying, picnicking on Blundell Sands and elocution lessons. At 16, she won a scholarship to Rada, after which she found regular work at the Royal Shakespeare Company and the National Theatre as well as on The Sweeney and Minder.

One day, frustrated by the flimsiness of the script she was learning, she submitted her own. Widows was broadcast in 1984, six years after she married Richard La Plante, an American musician. Both were desperate for children, but La Plante became a mother only last year, close to a decade after they divorced. Lorcan William Henry was born in July 2003 in Florida. La Plante, who had been on the books of an adoption agency for years, saw him when he was two days old.

With the help of her nanny, La Plante's productivity levels seem to be unaffected. At her home in Surrey, near Richmond Park, she gets up at 4.30am, as she always did, and writes uninterrupted for six hours. 'I have to stick to the same strict routine, I cannot deviate from it. They know not to contact me.' One day a week, she goes to Soho for business meetings. As much time as possible is spent with Lorcan.

'I think I probably could not have been a good mother earlier on,' she says. 'There's a calmness now. I'm so much more knowledgeable. And I work at home. We had a severe panic recently because he got stung by a bee and he's allergic to bee stings... I carried him at a run to a medical centre, because I was there. Whereas, before, I would have been at the prison, the path lab, with the forensic department. Now I've got a team and I trust them. When I was younger, I felt that I had to do everything myself. I was draining myself. I was so tired. But now, if I go to a play, I'm honest enough to say I might nip out in the interval and go home.'

She leaps up and does an imitation of Lorcan pacing, hands clasped behind back. He loves mobile phones, flushing lavatories, locking doors and feeding his tea to the Great Dane. 'He is a boy of all boys,' she says. 'I find everything about him amusing. You never know what's going to happen next. You sit down, thinking, "God, I'm exhausted", then he gets stung by a bee.'

The other night, trawling through the TV channels after Lorcan had gone to bed, she caught a show that, though obviously aimed at his age group, had an unexpectedly soporific effect on her. 'What's the name of the one with the rainbow?' she asks urgently. 'Where they go "Wheee-fphhhhh!" like they're farting? "Fphhhhh!" Boohbah ! Yes, that's it! It's like watching something when you're on drugs. I love it. "Fphhhhh!"' La Plante has never had much need for downtime before, but now she's starting to see its appeal.

&#183: Above Suspicion is published by Simon and Schuster, £17.99

&#183: Trial and Retribution: Blue Eiderdown is on ITV1, 11&12 October

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