In Japan, Germany and California the world’s biggest car manufacturers are pouring millions of pounds into what they believe is the future of motoring. With great fanfare they have shown prototype hydrogen fuel cell cars that emit only water, and promise to be selling them within a decade.

But unknown to many, Britain has its own environmentally friendly car of the future, already nearing completion in an unassuming building at the edge of Coventry’s ring road. It is government funded and built by a man whose previous achievements include constructing the robot R2D2 for the original Star Wars film.

"The internal combustion engine is dead," proclaims John Jostins, the brains behind the project. "We’ve had the car for 100 years and it’s time for a turnaround."

His Microcab is already operational but he hopes a commercially viable version, with four rather than three wheels, will be ready within a year. This would make it the first fuel cell car in the country to be sold on a commercial basis.

On the surface it all looks incredibly simple. Inside his three-wheeler is a hydrogen tank connected to an 8in-thick fuel cell the size of an A3 piece of paper, which creates power for a conventional electric motor.

"Fuel cells may not have the chrome and the pipes and the excitement of a traditional engine," says Jostins. "But that’s old technology. It’s a dying art."

Strong words, especially for someone who spent much of the 1980s helping to design rally cars and Formula One and Formula Two racing machines for the likes of Williams and Benetton.

Jostins founded Microcab Industries in December 2002. However, his notion of a silent lightweight pollution-free urban vehicle dates back to 1996 when he was designing futuristic modes of transport for Dennis Potter’s television drama Cold Lazarus.

"I remember it just suddenly struck me," he says. "I was travelling to and from the studio every day across London, rarely doing more than about 15mph, and I just thought it was completely pointless — all these big, powerful cars pumping out fumes for no reason. I was imagining vehicles such as a driverless, hovering taxi for Cold Lazarus and I just started to wonder what I could do in real life."

Jostins’s original idea was for a hybrid pedal/electric vehicle and he experimented with various prototypes before a Department of Trade and Industry (DTI) Smart award — a £45,000 grant given to companies to develop promising ideas — enabled him to incorporate new fuel cell technology into his vision for pollution-free city motoring.

Jostins, 49, has since been awarded a DTI grant of £125,000 with which he is developing a four-wheel version of the Microcab. The project is also supported by Coventry University, where he is a part-time lecturer in digital design.

The current Microcab, constructed in collaboration with Piper Design, the motor racing specialist, has already achieved many of his goals. Made from a mix of plastic panels and alloy running gear, it can travel at up to 30mph. The fuel cell requires few moving parts and virtually no maintenance. It can do 100 miles on one tank of hydrogen.

"There’s no exhaust, no catalytic converter, no spark plugs: none of the parts designed to clean up after old technology," says Jostins.

"I always think cars today are like old houses. We’re constantly adding things to adapt them to the modern world, but we don’t need to do that for cars."

The Microcab’s roof is lined with solar panels that can be used to generate additional power. It drives more like a moped than a car but couldn’t be more straightforward. The driver sits astride the centrally positioned seat, holding handlebars rather than a steering wheel.

A flick of one switch effectively turns the car on, then another switch flicks forwards or backwards, depending in which direction you want to travel. You twist the right handgrip to accelerate and grip the bike-style brakes to stop. Its four-kilowatt electric motor is the equivalent of about 5bhp.

However, weighing just 551lb (compared with 3,031lb for a BMW 3-series, for example), it accelerates remarkably quickly. This can be slightly unnerving on three spindly wheels, especially round corners. It reaches its upper limit of 30mph in eerie silence.

While the current model is Jostins’s proof that his ideas are a lot more than science fiction, he accepts that the three wheels and open sides means the car is unlikely to attract much commercial backing, despite interest from India and the Far East.

The four-wheel model currently in development is more conventional, with two doors, wing mirrors, a steering wheel and foot pedals. It looks like a cross between a new Beetle and a bloated Smart car. Jostins plans to have a working prototype completed by July 2005, followed by a fleet of 10 vehicles later in the year as part of a pilot project with a commercial partner. If that goes well, he’s looking to go into partnership with a big firm.

The designer is already in talks with one "major vehicle manufacturer", although he refuses to name names. "People think fuel cells are something for the distant future but it’s happening now," says Jostins.

"My advantage is that, because I’m not part of an established company, I can afford to be more creative. A lot of the car companies have too many vested interests to want to do away with the internal combustion engine."

Jostins hopes fuel cell cars will initially be added to fleets of vehicles operated by urban taxi companies, hospitals, the military, holiday resorts, universities or delivery companies, who could then justify their own hydrogen filling station.

"The internal combustion engine will be with us for a while yet," he says, "but the writing’s already on the wall."