Your engine starts hissing, smoke begins pouring out and the smell is enough to make your eyes water.

There must be something wrong with the car, most people would surmise, but for one Surbiton family the truth was far more shocking - there was a metre-long snake being cooked to death on the engine.

While driving her daughter to school, Lesley Muir, 36, was hit by a potent and unpleasant smell, which she later likened to somebody burning a burger on a barbecue.

There was smoke coming from the engine, so after stopping at Surbiton High School with four-year-old Flores, it was straight to Berrylands MOT, where the scale of the problem was realised.

A one-metre exotic snake, thought to be a discarded pet, had crawled into the engine manifold, where the heat of the engine had burnt it to an unsightly crisp. It was up to the mechanics to dislodge the unsightly mess - all free of charge too.

Mrs Muir, who lives in The Ridings, said: "It was the last thing that we were expecting. I think it is somebody's pet which might have escaped and then crawled onto the manifold to get away from the rain.

"Half the neck was still on the manifold. It had quite big fangs."

Colin McCarthy, reptile curator at the Natural History Museum, said: "The condition of the specimen is not good. Nevertheless, I am quite confident that it is a corn snake (elaphe guttata, recently re-named Pantherophis guttatus), a harmless species originating in North America, but kept widely as a pet and bred in captivity."

A week later and the smell of the sizzled serpent is still in the family's Renault Megane.

Mrs Muir, 36, said: "I think around here if somebody did set it free it could live quite comfortably because there are lots of gardens and it has been quite hot.

"We thought it must be some kind of animal but it was really a shock to find a snake.

"It was quite big. It's certainly the weirdest thing that has happened to me in quite a long time."