A mother left stranded after her one-year-old son ate a vital component of her car key managed to start the vehicle by holding him over the wheel, the BBC reported on its website.

The report said that a quick-thinking RAC patrolman suggested the ingenious solution after working out that toddler Oscar Webster had swallowed a radio transponder from the key.

The tiny part, which was only the size of an aspirin, managed to make contact with the car’s immobiliser – even though it was passing through the tot’s stomach at the time.

It has since re-emerged with no harm done to Oscar, the report said.

The BBC said the toddler’s mother called in the RAC when the car failed to start two weeks ago.

The first thought of patrolman Keith Scott was a flat battery, but that was quickly ruled out.

He told BBC News Online: “Then his mum remembered that Oscar had been sucking at the keys, and when we looked at them, the cover over the transmitter was off and the transmitter wasn’t there.

“It dawned on us that Oscar had probably swallowed it.”

Without the transponder, the pair were going nowhere, but Keith came up with an ingenious solution, the BBC said.

Working on the principle that that the transponder would valiantly continue to transpond – regardless of its environment – he put Oscar as close to the wheel as possible.

“His mum sat in the driver’s seat, and put him on her lap with his tummy pressed up against the wheel.

“We were amazed when she turned the key and the car burst into life.”

With the car started, the toddler could be returned to his seat and the journey completed, the BBC report said.