It’s a sunny morning and I’m bowling along the M25 with a bootful of clobber including folding chairs and a tent, plus three passengers. I’m also driving in bare feet. I’m not on my way to a hippy festival, but I am trying to prove that green is good by “hypermiling” my way to the south coast — squeezing the most possible miles out of a single charge of an electric car.

I’ve taken some tips from Wayne Gerdes, the world champion hypermiler, who knows better than anyone how to get most spark for your buck. Gerdes, from Tennessee, recently set a new record by driving 2,835 miles from coast to coast across America in a battery-powered Porsche and stopping for only two and a