Since August 1993 she has been working flat out on her latest three-part documentary, In the Company of Men, about the British Army in Ulster. Even now, a week before transmission, she is still tinkering with it. She rushes over to the desk and makes the editor replay the opening titles over and over to get sound and vision just so.
"I love doing this," she says. "I can't bear it not to be as right as it can be." More than two years' work for three hours' airtime - not a very productive ratio. But it matters little when the finished product confirms you, at the age of 36, as one of Britain's leading documentary makers.
Maggie Young, Dineen's long-suffering associate producer, takes a break from frantic administrative calls to smile indulgently at her producer/director. "Whatever I organise, you disorganise. But we get the results, and that's what counts."
It is indeed. Dineen's films - about such diverse subjects as a retired colonel in Kenya, Irish roadworkers and the Angel Tube station - have won awards and critical bouquets in equal measure. Her last series, The Ark, about London Zoo, picked up a Bafta. Paul Hamann, head of documentaries at the BBC, finds it difficult to contain his admiration for the woman he describes as "one of the best film-makers in the world. Some years ago, I was given the award of Documentary-Makers' Documentary-Maker and asked who I admired. The person I made number one was Molly Dineen - the future of British documentary-making."
What distinguishes her films is their humanity. She has been accused - on The Ark, for instance - of "going native" with her subjects, but her sympathy for their stories lends her documentaries a rare warmth. "She's got that unique ability to get under the skin of her subjects - especially men," Hamann says. "Whether it's men digging the roads or the more posh people in the Army, she has them eating out of her hand. No one else does that. In this series, she gets things out of Major Crispin Black that I've only heard from Republicans before - and yet he and the Army are still pleased with it."
Major Black, the likeable subject of "The Commander", the first in the series, explains how she does it. "Looking back on it, she has a very subtle and clever technique. She puts you at your ease. Once she's done that, she's able to get a more accurate picture of what we're like. People then relax for the camera."
Dineen takes up the theme. "Casting is obviously key, but what I love is to cement a relationship with a subject, to get them to have a rapport with the camera. When I first entered the officers' mess for this film, some turned their backs on me. They hate everything about you because you're a media bod. But after a few months, they see that you might have a serious purpose and that you're not just going to show them as the upper classes jumping over candelabras."
Unlike, say, Nick Broomfield (The Leader, the Driver and the Driver's Wife ; Aileen Wuornos: the Selling of a Serial Killer ; Tracking Down Maggie), she intrudes into her films without taking them over. No one- trick pony, she. Her persistent questioning, wobbly camerawork and shots of the boom microphone held by Sarah Jeans - the only other person in the two-strong crew - are all left in the final cut, but they enhance rather than overwhelm the subject matter.
She describes her style as "not fly-on-the-wall, but more of a grown- up home movie. People are just talking to me. It's a bastardised version of cinema verite. My films look accessible and commercial, but they're also informal. It's all hand-held camera. I'm not hiding the process."
From her teacher Herb DiGioa at the National Film School, Dineen learnt about "morality when it comes to documentaries". She abhors the now-fashionable documentary technique of stitching up interviewees (remember the Australian family's complaints about their portrayal in Sylvania Waters?). "It absolutely stinks," she says. "They reinforce the prejudices you already have. If they film someone upper class, they have to shoot up their noses with the family portrait behind the head, and if they shoot squaddies, the camera has to be looking down on them. Even by the way they intercut the film, they can stitch people up."
Major Black was aware of the dangers of allowing a film crew access. "Obviously, the Army's quite easy to parody. You can make anyone look a dick on camera.You can ask trick questions, or you can edit it to make it look all wrong. But we trusted Molly. I never felt we were going to get stitched up. That's not to say I like all of the things in the programmes, but we wouldn't have expected her to make a propaganda film for the Army."
After HMS Brilliant, Nautilus, Commando and dramas such as Soldier, Soldier, Civvies and Strike Force, Dineen and Hamann were worried about sending yet another documentary series about the armed forces marching into the schedules. Dineen justifies it by saying: "I have a new angle on the Army, which is to be positive. Before now, the attitude of the media has been to take certain institutions and attack them just because they're the backbone of the Establishment."
But her approach is costly. She admits to being "fantastically over budget" on In the Company of Men. Hamann affirms that "she has a certain cavalier attitude towards budgets, which causes me problems, particularly in these dark days at the BBC". But this producer gets special treatment. "The BBC never fixes my budget up-front," she reveals. "Secretly, Paul Hamann has an umbrella of money for three hours' film. I say it'll be 90 minutes, then it grows like a hideous disease and they're actually quite pleased." Hamann concedes that indeed "one forgives her all".
No one would claim that making films with Dineen is an easy process, however. Hamann says that, particularly in the editing, she wants to examine every permutation. "She'll ask 80 people their opinion, and in the end she ignores us all and does her own thing anyway."
After working with her on The Ark, according to Dineen, the executive producer, Eddie Mirzoeff, "decided life was too short" to team up with her again. Perhaps he had a point."We've been in the cutting-room since June of last year," Dineen sighs. She shot 80 hours, an exceptionally high amount of film, because, she says, "I don't direct when I'm shooting. I let the material dictate. It stems from pretty deep indecision, but also from wanting to follow tangents, which is often where the richness comes from. You want to follow not just the tree but the offshoots, too." The sheer volume of footage has seen off two editors. "With the third editor," she says, "life has been a dream."
As she turns on the charm and gives you her undivided attention, it is not hard to see how Dineen wins people over. Hamann says with an exasperated laugh that "she's completely impossible to work with. She drives me up the bloody wall," before adding, "but I love her to death."
"The way I make films is like socialising," Dineen says. "It's party principles. If you like them and they like you, it's going to be a better film. I don't see the point in looking sour and asking a list of set questions. It's an extension of how I've always been - which is very interested. Some people are just naturally curious. It's just me at one big party with my camera."
`In the Company of Men' begins on Thursday at 9pm on BBC 2.