19/07/2008 07:58. To the casual observer, it looked like any other petrol-guzzling Chelsea tractor driven by a mother clogging the streets on the school run. This, though, was a 4x4 with a difference, one that even the most committed tree-hugger would be proud to drive.

It emits water from its exhaust fit for drinking and glides along in near silence. It is one of the world’s first hydrogen cars and, according to its makers, the future of motoring. It also costs half a million pounds.

“We started working on fuel-cell technology in 1996,” said Brian Johnston, the senior project engineer for electric and fuel-cell vehicles at Nissan. “In this prototype, there is a hydrogen tank under the back seat, a fuel cell under the driver’s seat and it takes 3-5 minutes to fill up. It is a reasonable fuel... // Times Online