BMW 7-Series

The car is familiar - but what's that in the boot? Last week, Auto Express put Mazda's hydrogen-powered RX-8 coupé to the test - and now, BMW's 7-Series appears set to follow in the Japanese machine's wheel tracks.

A concept version of the German firm's zero-emission CleanEnergy car has already debuted, but our spies spotted this production variant being worked on and tested in Germany.

The model's huge hydrogen tank fills the vast load area, and is the tell-tale sign that this is no ordinary 7. Under the bonnet, the clever V12 engine is able to run on both petrol and hydrogen, and switches automatically between tanks when one or other hits empty. This powerplant is a development of the 231bhp 6.0-litre 12-cylinder unveiled at the 2003 Frankfurt Motor Show.

BMW has committed to delivering the first roadgoing hydrogen versions within the existing 7-Series' lifespan, so they are expected to go on sale in 2008. Initial examples are likely to be aimed at small fleets, which will provide feedback to assist the company in its development of the technology.