Molly Dineen: Notes from the underground

My career has been a series of happy accidents," says Molly Dineen. "I was always interested in people. And when critics talk about the way I interview people in my films, it's purely how I'd behave if I'd met someone at a party. I was always a nosy bastard."

Nosiness has paid off richly for Ms Dineen, the leading British documentary-maker of her generation. Her films are gimmick-free inspections of British institutions under threat of change or extinction, and of the characters who embody them. Her camera watches faces, conversations and behaviour patterns with a seemingly incurious objectivity, allowing her subjects to unveil their secret fears and frustrations. "I'm really a wildlife film-maker," she says. "I'm going to sit and wait and really hack you off by becoming part of your life, saying, 'Ooh thanks, I'll have a cup of tea too, thanks.' It gives you a better quality of contact with people."

She made her name with her first feature, Home from the Hill, about a retired cavalry officer, Lieutenant-Colonel Hilary Hook of the 7th Hussars who, after half a century living in sun-drenched style in India, Sudan and Kenya, comes home to England and tries to adjust to life in Wiltshire without servants, cook or elephant gun. Her camera watched as the Colonel wrestled cluelessly with electrical devices and grimly filled his Safeway trolley with gin and brandy. It was a touching look at the British imperial sunset, examined through a (mostly) sympathetic survivor. The film was shown on BBC2's 40 Minutes in 1987, won Dineen rave reviews and turned the fruity-voiced colonel into a national talking-point. He received fan mail from ladies d'un certain age, offering to come and keep house for him, after he muttered, on camera, "a big fat woman, that's what I need..."

A year later, with My African Farm, Dineen returned to Kenya to film the colonial household of Sylvia Richardson, another British diehard. Heart of the Angel (1989) was a wonderfully stark look at the inhabitants of a decrepit London tube station. A four-part series, The Ark, followed the staff and animals at London Zoo as their livelihood was threatened by cuts. It won a Bafta in 1993. Later, Dineen helped Tony Blair win the 1997 election with a 10-minute film that showed him chatting about his youthful ambitions and talking politics with his children over breakfast. Dineen also filmed Geri Halliwell for several months as she prepared to quit the Spice Girls; the 90-minute documentary, Geri, showed the singer being interviewed on the lavatory and experiencing what seemed to be a nervous breakdown.

This year, Ms Dineen gets a handsome accolade from the British Film Institute: a three-volume collection of all her films on DVD. The first volume, out on 25 April, contains Home from the Hill, My African Farm, Heart of the Angel and In the Company of Men, her three-part examination of Welsh Guardsmen on a final tour of duty in pre-ceasefire Belfast.

We met at her rambling house in west London, where she lives with her husband, William Sieghart, the contract printer who administers the Forward Prize, and their children, Maud, Ruby and Joe. She cooked us lunch and we sat under an apple blossom tree, looking down the garden at the conservatory where she is editing

the extras footage for Box Set No 2. She is an impetuous talker, funny, warm and confiding. At 52, there is still a touch of the madcap fifth former about her.

Dineen was born in Canada but grew up in Birmingham. By her own account she was a wild kid, writing on school walls and smoking by the railway line. Why did she misbehave?

"My line to the headmistress was always 'broken home' – it went down well in those days, because so few people's parents got divorced – but we weren't witnesses to conflict; it was quite an amicable set-up. Probably I was just a horror." Her father suggested that she should leave school and study something she was interested in. "So I went to the Bourneville School of Art and did photography. I came to London and moved in with Daddy and his new girlfriend, Shirley Lowe, the writer. Shirley was fabulous, a real journalist with a conscience."

Through her stepmother's contacts, Molly found work in a photographer's studio, did an apprenticeship, put a portfolio together and sailed into the London College of Printing.

It was there that she experienced a kind of epiphany. A committed exhibitionist ("I was one of life's performers, in a gold trouser-suit, in a rock band,") she met "these really groovy people – Boy George, Stephen Jones, Kim Bowen, Stephen Linard – who all lived in a squat in Warren Street. We became good friends. But for them showing off was a job, and they did it brilliantly. After I met them, I never did any dressing up again. I spent the rest of my life in slip-on shoes and a kilt, watching people."

Why did she move, at the College of Printing, from still photography to movie-making? "The teachers. The film tutor was fabulous – Bob Morgan, an American, he smoked a thousand Kent cigarettes a day, talked very fast and made you feel you were in the film industry. His classes were inspiring. Photography was taught by a retired wedding photographer from Wales and it was all about bellows extensions and studio lighting. I found it dementing."

At the National Film and TV School, a classic "observational" approach to filming was drilled into her by Colin Young, the founder, and Herb di Gioia, the American documentary chief. "Herb's films involved one wide shot of a man making a chair," Dineen says. "The observational school was full of principle: no commentary, no cutaway shots to people sitting on sofas, no set-ups, no music." Once, when Dineen was fool enough to write a script, Di Gioia held it up to ridicule before the class. "He was very strong-willed and I fought against him, but I discovered it was far better to go with the flow of life than to divide it up into shots."

Though she is proud of Home from the Hill and My African Farm, she talks most energetically about Heart of the Angel. "It was my first-ever proper commission, selling an idea to the BBC," she says. It was a tough sell – a documentary about the glumly eccentric staff at a scabby tube station that was about to be closed for renovation. It started when she met John McGlade, who worked in the London Underground signals department, on a South American trip. Back home, he invited Dineen to an unusual event.

"They were having a party, with drinks, nuts and biscuits, on the platform at Great Portland Street station at 4am. I was sitting in a deckchair having a laugh with John, when out of the tunnel came this gang of men and women workers holding a rail that had been put on the wrong way round. I couldn't believe what I was seeing. Some of the men were singing – black men with gold medallions, singing beside naked flames."

Never an artist to do things by halves, Dineen spent six months haunting the night-time tunnel-cleaning trains, discovering the existence of bands of female "fluffers" and Irishmen with picks and shovels, cleaning and carrying out running repairs on the sleepers in the dark. In the film, the viewer feels like an explorer discovering a lost tribe. "I thought the tools'd be more modern than a pick an' shovel," says one Irishman. "'Tis like the 18th century down here."

Indeed. As the staff became accustomed to Dineen's camera, they opened up. The station boss revealed a passion for painting watercolours of English canals. The born-again lift operator decided he would rather be a preacher, "to tell people the truth". The grumpy ticket clerk, who callously advised foreign travellers to use "the Pickly-Dickly Line," started to consider his life: "I'd like to have been taller. And I'd like to have had a better education, so I could appreciate literature and art."

Dineen doesn't mind critics calling her work political, "but for most of my documentaries, if I'm really honest, I'm trawling around in the ballast. I'm too entrenched on the bottom level with the people who work there, to see the overview. Now I'm old and grey, I can read the papers and think, 'Ooh, that's a wonderful example of Thatcherism,' or whatever."

Your Angel film, I say, was full of elemental images – travellers descending into hell, walkers on the endless spiral stair like the damned in Dante's Inferno, the station boss listening out for The Last Train Ever. Didn't you feel like making more of them? "I think it pays," says Dineen, dryly, "not to be too journalistically busy."

Her most recent film, The Lie of the Land (2007) was much more polemical – a haunting insight into the changing economic fortunes of country people hit by the hunting ban, in which Dineen discovered that healthy calves were being slaughtered because it cost farmers too much to rear them.

"Yes, you're right, it's a much more overtly political film," she says. "I was in such a different place when I made it. I was so furious about everything. I felt I knew at last what was going on in England and it made me furious, so there's an enraged voiceover through the film."

But one thing has never changed through Dineen's career – her ability to charm reluctant people and draw out their secrets, to make them feel her sympathy and warmth. She has always taken the lost, the beleaguered, the crusty, the neurotic, the desperate, the self-doubting and the sad and subjected them to her firm but tender enquiries – a voice behind the camera lens – until they confide in her. In a word, she mollifies them. That is Ms Dineen: Britain's No 1 camera-toting mollifier.

'The Molly Dineen Collection Volume 1' is out now on BFI DVD