Eager owners sometimes present a Toyota Prius as David Attenborough on wheels - decent, environmentally aware and beyond criticism. And yet there are nagging doubts that the Toyota is not nearly as irreproachable as Britain's national treasure. You don't have to look very hard on the web to find American buyers questioning the official fuel consumption figures, while some Europeans question whether a simple diesel engine would not be equally economical.
So, we decided to conduct the ultimate test, pitting the Prius (easily the world's biggest-selling hybrid with just over 1 million sold to date) against the devil's own tool; an SUV. Our choice of SUV was simple. Jeep was recognised in 2007 for having the most improved fuel consumption across its model range, and has won a Green Award for the Patriot. The Patriot Diesel is one of the most economical 4x4's available on the market today (thanks to its VW engine) and boasts lower CO2 emissions than, say, a Renault Scenic 1.6.
The rules would be simple; both drivers were to drive the way they normally would, but in order to ensure that driving styles didn't interfere with the results, they would swap half way and all speed limits would be adhered to.