ON MY WAY to interview Detective Chief Inspector Jackie Malton, one of the highest ranking women in the Metropolitan police, it struck me that I looked like an off-duty policewoman myself. Polished navy flatties, navy tights and skirt, discreetly checked camel and navy jacket . . . hang on, I thought, I don't usually dress like this: what am I doing?

I realised that I had unconsciously picked clothes designed to ingratiate me with DCI Jane Tennison: the brisk and formidable heroine played by Helen Mirren in Lynda La Plante's television drama, Prime Suspect. Tennison was a driven station head sacrificing her personal life to the brilliant and ruthless pursuit of villians. Lynda La Plante said at the time of the first Prime Suspect, 'The professional character of Jane Tennison was based on a London DCI I met during my research who had gained extraordinary respect from her male colleagues because she ate, slept and breathed the job.

'As officers jostle to get to the top, there is certainly prejudice against women. If two detectives are on the case, a man'll open the door for the woman but it'll be the back door, because he wants to be in the front, where the power is. A woman must be stronger than men to survive in such a world, but she mustn't lose her feminine insights.'

What I encountered, however, when I met her role model, Jackie Malton - upon whom the fictional DCI was based - in the Green Belt village where she lives was a very different kind of police officer. Today DCI Malton is a community liaison officer: still a woman dedicated to her job, today her difficult task is to keep open an honest dialogue between the police and an ethnically mixed community in London.

It must be maddening for a woman who has been so successful in her own right to find herself best-known as a fictional character. So, was it even true?

'I don't know who else she met but certainly she and I worked on the script for months and months. The plot and the character were hers, but the authenticity was mine. We had to make it real in police terms and so the character became more 'me'. I'd tell her something one day and the next day it'd be in the script.'

Jackie Malton may be responsible for Prime Suspect's gritty authenticity, but she is not a typical woman police officer. At 42, she looks like a grown-up Princess of Wales. The day we met she looked confident and successful in an emerald green jacket and classy gold jewellery.

It was a surprise, then, to hear her say, not once but several times, that she had suffered from low self-esteem most of her life. 'The 11-plus caused me a lot of emotional damage. I felt society had written me off. I had failed. Years later I heard that because more girls than boys passed the 11-plus, they used to mark down the girls and I thought, if I could prove that was true, I'd sue the government for the harm and pain it caused me.'

She was born in Lincoln in 1951, where her father was a manager on Associated Newspapers' provincial titles. And her mother? 'She didn't work. It was that era.' Her mother wanted Jackie to go to a private school, a convent. 'I thought to myself, I'm not going. We had to sit an entrance exam and I just put 'Don't know' after every question. Even at that age I knew I was a rebel. I used to play football with two boys in our road and apparently I said to my mother, 'How are nuns going to play football in those long frocks?' '

She went instead to a secondary modern school and emerged with O-levels but not enough academic qualifications to do what she really wanted, which was to be a probation officer. 'As a kid I'd done a project on the Howard League for Penal Reform and I was fascinated by prisons and the underdog. But I thought prison officers walked around with a bunch of keys and locked people up, and I didn't want that. So I went into the police force.'

Her rise was rapid. She started her career as a cadet, straight from school, in the Leicester force. 'In those days women police officers were in a completely separate department. We had to deal with women's issues. I was 19, and I didn't understand things then as I do now. If I went to a domestic (dispute) and sat them down with a cup of tea to talk it over I would leave thinking I'd done a good job. That's how nave I was]'

After nine years, she moved down to London where she was accepted as a detective sergeant. She was seconded to the 1981 Deptford fire investigation after 13 black teenagers were burnt to death during a party. 'Those images, unfortunately, have always stayed in my head and whether that's a character defect, I don't know. At the Deptford fire . . . that boy hanging out of the window . . . I hate it. I wish they would go away. It was a terrible, terrible thing.'

There was an inquiry afterwards. A racial motive was suspected, but never proved. 'That inquiry taught me a lot about the system.' Next she moved on to the team investigating criminal aspects of the Brixton riots. Already Jackie Malton was an untypical police officer; politically incorrect within the force, with a passionate and inconvenient sympathy for the underdog.

She joined a Flying Squad as the only woman among 40 men, working on armed robbery prevention. Promoted in 1984 to detective inspector, she was posted to West End Central and then transferred to the Company Fraud Squad. In 1989 she went from there to Hammersmith as its DCI: the woman in charge, the Helen Mirren figure. For the next two-and-a-half years she was her job. 'I was all-consumed with the police, and that's not particularly healthy.' Jackie Malton was destined for the top. Even so, she suffered from traditional police attitudes towards WPCs. 'I felt I was equal and the system should allow me to be equal, and it didn't. I went out on the beat and was always good at that - I'm quite intuitive. I was,' (she says this at least three times in the course of our interview, with growing emphasis), 'I was a good police officer and nobody can take that away from me.'

Her next choice of job was a surprise. In November 1991 she applied for, and got, her present poisition as Kensington and Chelsea's Community Liaison Officer: a job seldom held by a detective, but absolutely right for her.

What led her from such high-profile work into the apparently soft option of community relations work? 'I'm good at the chat, at relating to people: that's why I applied for the job. It's a new culture for the police, that we sit down and listen instead of always thinking we're right. We were often wrong. You have to acknowledge your mistakes and their anger. You don't win people's trust overnight.' No one, she thinks, is born evil. She has compassion even for wife-beaters and abusers.

'They are dumping their own low self-worth on to someone else. It's about power, control, domination, to hide their own inadequacy. You've got to acknowledge the pain of the victims, but you also have to treat the offenders as individuals, not just people who've done something criminal. I don't believe the answer is to lock people up.

'The trouble is, we're - the police, this society - obsessed with what we can measure, like the clear-up rate. How do you measure the value of talking to someone for three hours and making them feel better? But if you fight for the minority, the majority turns on you, and it has an effect. You think, if you're the only voice you've got to be wrong. You end up frustrated and angry.

'In this country we treat the symptoms. We put people in prison and write them off. There has to be a prison system for the worst offenders, but once they're there we ought to provide more facilities. I've met loads of women in prison and they say, 'You treat me like an animal and I'll behave like one'.

'I've always fought for the underdog and I'd love to have been an MP.' She grins at her idealism, after all these sobering years 'Not that I would have done much good]' Such views have incensed colleagues.

Last August, after years of overwork, stress, too many cigarettes, a bit too much alcohol, she found herself with a racing heart, hyperventilating. 'I couldn't walk down High Street Kensington, the stress levels had got so high.' Eventually she suffered a panic attack so severe that she thought it was a heart attack and she was dying.

'When you're taken ill it forces you to sit down and think, crikey] If I'd carried on my life the way it was, I would have died. But I believe I've been given time out to reflect and change. For somebody who'd given the world this front, it was a shock.'

Jackie Malton shares her picturesque whitewashed cottage with two long-haired tabbies (both male), William and Daisy. She hates them to catch things and had just spent ages rescuing a hapless mouse. The mouse was outside recovering; the cat sprawled on a forbidden sofa, registering displeasure. 'Oh Daisy,' said her owner, 'You know you're not supposed to lie there.' Daisy stayed put. Not a strongly authoritarian character, this DCI Malton.

The living room displays dozens of photographs, including some from the Prime Suspect awards ceremony. There are serious books, mostly by or about women or crime, towards which she is unnecessarily self-deprecating. She wonders sometimes what motherhood would have been like, but does not regret never having had children. Her job has left too little time for relationships, although she says she has many supportive friends.

She says that at last, in her early forties, she feels sure of her identity and place in the world. She has taken positive steps to reduce the stress. She goes to Alexander technique classes, for which she has nothing but praise, and has given up drinking. She is easy to talk to, funny and informal and honest. Only the cigarettes remain. 'Can't give up everything at once]' she said defensively.

Jackie Malton is a member of the Committee for Women in Prison, run by ex-inmates, which has taught her a lot. 'You give me those women, of that calibre, and compare them with the rich wives who waste their money shopping in Harvey Nichols. Yet those women would just write off the ex-prisoners.' Contemptuously, she imitates a spoilt upper-class whine. Yet, invited to join a group for high-flying women called Forum, she is thrilled to find herself among them. 'I love strong women. I didn't get my strength from men, I got it from women.'

She feels she was underestimated in her job and that her potential was stifled. 'I do have some loyalty to the police, because over 20-odd years my experience has made me what I am; but at last I can say what I really always wanted to say; I needn't think, oh God, does the commissioner approve or is my career finished?'

She dares to say anything these days. When I asked her about violence within the force she agreed that it was a problem.

'I worry about the release of aggression that men need. We are in a position of authority and power over people's lives. Wife-beating is very high in the police force. We've just had a series of seminars dealing with domestic violence and I'm told that in every seminar the issue of police violence against their partners was raised. In my day it would never even have been put on the agenda. On the other hand, there is a navety on the part of the public towards the police. If you go to arrest an armed blagger you don't knock on his door and say 'Good morning'; you kick the door down because you know he keeps a gun under his pillow.

'When Prime Suspect came out I was afraid people would say, 'But it's not really like that'. It's painful for me to watch because that's my experience, I suffered that prejudice, and if other women in the police say they didn't, I say they're liars.'

She will retire in seven years' time. 'Oh God, yes] Yes, definitely. I retire at 49 and then I'm off, I tell you. I've done my bit.' And then? 'I'd like to work with ex-offenders, do more work around issues affecting women and if possible, advise for TV on scripts.

'That's another thing I got out of Prime Suspect . . . I've tapped into my own creativity that I never knew I had. I type stuff out on the word processor now, and I'm creating ideas and concepts - I sold a story-outline the other day. All that came out of the collaboration with Lynda La Plante. I believe that Prime Suspect was meant to be. For me, it was more than just a television programme.'

(Photograph omitted)