A pioneering hydrogen-fuelled engine is among the many 'green' cars on display at the British International Motor Show in Birmingham, which is celebrating environmentally friendly developments in motoring technology.

And the BMW 750hL, which is making its UK debut at the show, has been attracting keen interest among visitors, many of them curious as to why the company has opted to use the combustion engine rather than develop fuel cell technology for the future use of hydrogen.

The luxurious long wheel-base BMW 7 Series houses a conventional 5.4 litre internal combustion engine, but instead of being powered by petrol, the tank holds super-cooled hydrogen which can be generated from water using solar energy, ultimately leading to zero-emissions.

"We are unique among the major manufacturers in banking on hydrogen powered internal combustion engines now for our cars in the future," explained BMW regional technical manager Lloyd Truman.

"Many companies are promoting fuel cell engines which ultimately make the vehicle an electric car and fundamentally affect the drive performance."

In fact, some of the BMW hydrogen saloons are the first series-produced cars to feature a fuel cell for supplying on- board electricity, according to BMW, but a 12-cylinder engine will drive the car.

"At the moment both technologies face the lack of infrastructure to use hydrogen, but the 750hL's engine can also be run as a petrol and hydrogen bi-fuel car," Mr Truman added.

The first hydrogen filling station was opened at Munich Airport in Germany last year and a number of 750hL models were used as shuttles during Expo 2000 in Hanover.

Mr Truman added: "The technology should achieve zero-emissions, while the internal combustion engine allows a conventional performance offering a spontaneous, dynamic and independent drive. This is crucial to maintaining our mission to offer the ultimate driving machine."