Business is booming for British bicycle-maker Brompton -- but it\'s cyclists in Asia who are snapping up its nifty folding models in their droves. In a world where outsourcing has become the norm, London might not seem the most obvious place to mass-produce bicycles. But that is where Brompton manufactured 36,000 bikes last year -- and it shows no sign of slowing down. \"We\'ve been growing for the last eight years at about 20 percent a year. That means we\'re doubling the size of the business every four to five years,\" managing director William Butler-Adams told AFP. Casually dressed in jeans and a polo shirt, the 38-year-old does not look like the average high-flying executive -- but many bosses would be envious of his figures. A quarter of a million Bromptons have been sold already and the company has a turnover of £20 million ($32 million, 23 million euros) and net profits of around £2 million. But their bikes don\'t come cheap. Retailing at £900 on average and beloved by trendy urbanites in cities across the globe, they are assembled to order in the firm\'s sprawling west London factory. \"We export nearly 80 percent of our bikes to 42 markets around the world,\" Butler-Adams told AFP on a tour of the complex, where workers -- their shirts emblazoned with the Union Jack -- are welding, polishing and building bikes. Style-conscious Japan is Brompton\'s biggest foreign market, while the folding bikes which can take the strain out of commuting have also enjoyed a boom in popularity in South Korea. The company made its first foray into the Chinese market in September. Undeterred by China\'s status as the world\'s largest bicycle manufacturer, it opened a store in Shanghai, hoping to attract wealthy commuters with its high-quality models -- and deter Chinese buyers from buying imitations. Nevertheless, Butler-Adams insists the fiercely British company will not cave in to pressure to cut costs by moving production overseas, or lowering its standards. \"If we went to China, on paper you would think we could make it cheaper,\" he said. \"But with the amount of support which would be needed, and the time and energy to try to manage things so far away, I suspect it wouldn\'t be cheaper.\" The main reasons for keeping the factory in Britain are linked to intellectual property, he added -- copies of Bromptons can be seen in cities across the world and especially in Asia. The company has come a long way since 1975, when founder Andrew Ritchie, an engineer by training, started sketching out designs for a folding bike. It was the view from his apartment, which overlooked the imposing Brompton Oratory church in London\'s South Kensington district, which gave the brand his name. But for many years, turning the bicycle from a sketch into reality was an uphill struggle. Established brand Raleigh rejected Ritchie\'s prototype, so he decided to produce the first Bromptons himself -- but it took 10 years for the business to find sustainable funding. It made 5,000 bikes in its first batch 12 years ago. Crucially, Ritchie, Butler-Adams and their employees own the company, so, he explains, \"we don\'t have some venture capitalist saying, \'come on, there is money, tons of money -- expand, expand\'\". \"We don\'t want to be like a child in a sweet shop... and then screw up the very thing that is what the business is about -- which is making a bloody good bike.\" Brompton\'s quality control is almost obsessional. Every tiny detail is checked, and checked again, before a bike is declared fit for sale. The company has several new projects in the pipeline, and has been working for five years on a folding electric bike. But Brompton is more patient than some of its traffic-dodging customers, and insists on taking its time with the designs. The new model will appear \"when it\'s ready\", Butler-Adams said. \"We could have sold something two years ago but it would have been rubbish.\"