So you fancy an eco-friendly(ish) supercar but, surprise surprise, no one makes one. What do you do?

Have one designed and built specially for you, of course.

Well, you do if you're Jay Leno. This hulking beast is the brainchild of the American talk-show host, owner of probably the best private car collection in the world and the most distinctive chin in show business.

When Leno and his chief mechanic (yes, he has his own chief mechanic) were chatting about the possibility of a turbine-powered supercar, they sketched a couple of designs on the back of a napkin.

Enamoured by the scribblings, Leno convinced California's GM design department to take the study and turn it into a working car.

And this is what they came up with: the EcoJet.

Making its first public appearance at this week's SEMA show in Las Vegas, the mid-engined supercar is powered by a Honeywell LT-101 turbine engine that runs on bio-diesel fuel.

The engine sits in a modified Corvette Z06 aluminium frame, clad in a carbon fibre/Kevlar shell.

The Corvette influence is clear in the squared-off muscular design, which GM designer Ed Welburn says was inspired by aeronautical and jet-age influences.

There's no word on performance, but with 650bhp and 400lb ft of torque on tap it should edge a Toyota Prius in a straight sprint.

If you like the look of the EcoJet, tough. It's a one-off design... but even if GM were planning to make a few more of them, we're betting the EcoJet could only be afforded by, erm, US talk show hosts.

The EcoJet isn't Leno's only modified toy, though. Last year we caught up with Jay so he could show us round his Tank Car - a 1600bhp chrome dragster powered by a Patton tank engine. See what we made of it here.