We meet in the cavernous depths of a Covent Garden post-production company, Complete Video. Although it's not yet 9.30am, Ms Dunlop is engrossed in a fierce snooker match with a bunch of male colleagues. She's spent the past two days with them, shooting the video for girl-band T-Shirt's debut single. The track, out next week, is a cover version of "You Sexy Thing". The video is a stylish spoof of the Seventies TV classic Charlie's Angels featuring the T-Shirt girls' mission to find their lost partner. Errol Brown, lead singer with Hot Chocolate, who did the original, makes a surprise appearance at the end as "Charlie".
Grabbing a packet of Marlboro Lights, Sara breaks off from the game to talk, before diving into an edit suite for a further four days' work. She is slight, boyish and dressed in a plain, long-sleeved T-shirt, black cords and the obligatory Nike trainers. But looks can be deceptive. She is opinionated, articulate and a frighteningly-straight talker, all too aware of the precarious nature of her chosen career and (of course) its potential rewards. "I want to work on the top style commercials - the biggest sports brands, drinks, cars and beauty products," she declares, lighting a cigarette. "Then I want to crack films."
Ms Dunlop confidently explains that she has always wanted to direct films. "When I was 12, I wanted to be loads of things - an archaeologist, doctor, lawyer - until I realised what I wanted to be was what I saw in the movies. So I decided I could be all these different things if I made the films." Persistence, contacts and luck have got her this far. With no family links with the industry ("Just cool parents who let me do what I wanted to do"), she grew up in south London and began making her own films on Super 8 while still at school. Next came a film degree at the University of Westminster. That gave her the technique, although she became jaded by the college's career advice. "Everyone at film school thinks film. They weren't dealing with where the bulk of the work is today - commercials and pop promos, which are an ideal grounding."
So, rather than follow her contemporaries into the industry by working as the lowest of the low - a runner - she teamed up with a lighting cameraman and began shooting her own ads. The pair approached Panavision for support and were loaned a 35mm camera free of charge. They then begged favours from other suppliers, facilities and wannabes eager to show off their potential for no pay. Dunlop wrote and directed her own commercials, including a moody monochrome ad for Dolce & Gabbana and an artfully shot sequence featuring a cellist for Pioneer.
Through this twilight world of freebies and favours, Dunlop met Eugene Ruane, then a creative at Saatchi & Saatchi. She begged him for a spare script and struck lucky. Their budget film for Fuji, featuring a mouse running full pelt into a photo of a mouse hole held by a crafty cat, was used. As was another she directed criticising high street banks' involvement in Third World debt, written by one of adland's top creatives, Dave Trott. "If you don't ask, you don't get," she explains, lighting up another cigarette. "I'd heard he was looking for someone cheap to do it, so I rang him and said `Why not me?'"
Trott, in turn, put her in contact with commercials production company Annex, whose recent credits include ads for the Renault Megane and Walker's Crisps. The managing director, Fred Robinson, signed her up on the spot. "It was easy to see she was going to be good," he claims. "You're always looking for someone able to bring something new. Sara's films have a modern look." It's about more than making a film that's nicely lit and well-executed, Robinson explains. "Each ad has a definite feeling - a particular mood." And luckily, Sara's still young enough to be influenced by different sources and techniques - "she's not set in her ways".
Dunlop has been based at Annex for the past year directing ads for Reebok, Elida Organics hairspray and Di Saronno Amaretto liqueur. "Anyone can start in commercials directing, although not anyone can succeed," she claims. "You see, it's not about working your way up. Few assistant directors become directors - you have to show them you can do it. It's an expensive business." She's not joking. With an average commercials budget anything between pounds 100,000 to pounds 300,000, the director must not only meet creative expectations but bring the film in on budget and on time. They must also manage the expectations of agency creatives, account managers and senior executives as well as the advertiser - all of whom can turn up on set at any time.
Quite a task, then, for a 23-year-old woman when people expect to be dealing with a seasoned fortysomething and, 99 per cent of the time, a man. Of the ad industry's 100 or so established "name" directors, there are only three women. "Shoots are generally very laddish," Ms Dunlop concedes. "All camera operators and lighting crews seem to be men. All creatives are into football and beer. While they're great to work with, at the end of the day they'll always step to one side to share a dirty joke." Not that she thinks this poses much of a problem: "I'll admit it, I make use of being a woman ... and my age. If you make a point of going up to everyone, shaking their hands and having a chat you soon get that fatherly thing going - which is really the best way to play it. It gets them doing things for you."
Often, she spends the first 10 minutes on set without revealing her identity - most people assume she's the PA. The jury's out on whether this trick has won her friends or enemies. But her age, she admits, has undoubtedly counted against her. "I'm sure I've lost jobs because of it, and because I'm a woman. But I hope when people see me walk into a room they see the possibility of a fresh approach, or a different angle on the job." And, of course, that they'll remember her. "I'm young, a woman and half-Chinese. I think I've more point-of-sale value than many other directors," she astutely declares.
Ms Dunlop may be right. But she'll need more than the gift of the gab and technical competence to make it big. "A good director must also have an ability to get on with people," cautions Geoff Smith, a copywriter at Reebok's advertising agency Lowe-Howard Spink. "No one in this game wants a prima donna." There'll be plenty of time for that sort of thing later. In Hollywood. Well, that's the plan