A narrow door between two restaurants in the heart of Soho hides one of the advertising industry’s biggest success stories of the past year.

Although it is located in the traditional home of British adland, it is far removed from the glass facades and airy receptions filled with modern art that are typical of most advertising agencies. The headquarters of Fallon London are merely the first sign of its individuality.

Fallon London, owned by French advertising giant Publicis, is a relatively small agency with only 173 employees, but it created some of the most memorable and innovative ads of 2007.

When Cadbury’s Dairy Milk was losing its market position, the agency turned to a drum-playing gorilla to boost visibility of the chocolate bar. Then there was the Sony Bravia campaign that featured plastic balls bouncing in San Francisco, colourful bunnies hopping in Manhattan and paint exploding from blocks of flats in Glasgow. Fallon also decided that hiring master confectioners, bakers and bricklayers to create a Skoda Fabia cake would be the most effective way of marketing the car.

“It’s not about being big in this industry. It’s good to be fleet and nimble,” says Laurence Green, co-founder and head of the agency.

Fallon was founded in 1981 in Minneapolis, where co-founder Pat Fallon developed his philosophy of “out-smarting the competition rather than outspending them”. By the mid1980s it was one of the top independent agencies not based in New York.

Mr Fallon saw no need to be with other agencies on Madison Avenue, believing that the heart of the Mid-west prairies was more suited to the group’s desire to be different. When he made his first move overseas in 1998, he was also keen to avoid the UK capital and wanted to open offices in Dublin, but the search for the right founding partners led him to London.

Mr Green believes that the agency has maintained this independence since the acquisition by Publicis in 2000, saying the owner leaves it alone to do its own thing. “We’ve done some of our best work since Publicis acquired us, starting with transforming the Skoda brand in 2000,” he says. “Maurice Levy [the chairman and chief executive of Publicis] rarely intervenes, seeing us as the creative mavericks in his portfolio.”

Hiring young, international creatives and ensuring that everyone is “bilingual” – meaning they have an equal understanding of digital and traditional advertising mediums – is crucial to the agency’s success, says Richard Flintham, creative partner. “We’re like the League of Nations – we have creative teams known as ‘the Swedes’, ‘the Latvians’ and Juan Cabral [who was responsible for the gorilla] is Argentinian,” he says. The average age at Fallon is about 26 and would be younger if the executives were excluded, adds Mr Green, 41.

The agency may be young and in touch with new media, but it has kept faith in television. Fallon’s aim is to combine new and old, making television adverts that are entertaining enough to be carried on to video-sharing websites such as YouTube. Cadbury’s gorilla advert has had more than 7 million hits on YouTube and when the Sony bouncing balls were being shot in San Francisco, pictures quickly appeared on photo-sharing site Flickr. “Television campaigns of the past had a beginning, a middle and an end. YouTube and similar sites have given them astonishing longevity,” says Mr Green.

Another element vital to the success of any agency is to have client marketing heads who are open to off-the-wall ideas. Fallon found this quality in Sony and Cadbury, but says it has turned away many clients. “In our first 18 months we declined to pitch for Express Newspapers and Mitsubishi,” says Mr Green. Fallon also says it has turned down eBay, Oxfam, The Telegraph Group and sausage-maker Walls for reasons that include time restraints and a “lack of desire for creativity” at certain companies.

Some industry insiders say the group attracts clients that share the need for radical brand transformation, with Skoda its greatest proof of being able to achieve this goal.

Fallon is through to the final two in the pitch for a major marketing blitz by Microsoft. Knowing it will never have Apple’s style credentials, Microsoft wants a new image focused on its reliability.

“We’re terrible at the pitch circus . . . awful schmoozers,” says Mr Flintham. “With Microsoft, we’ve been straight, honest and tried not to overpromise.”

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