Geoffrey and Hilary Herdman drove their 1956 Bristol 405 Drophead Coupé for 33,000 miles across the prairies of Canada, the deserts of Australia and the Andean mountain passes with their beloved vehicle suffering hardly a scratch.
Then they left it in the car park at a Sainsbury's in Sussex. "I was just walking back towards the car and I thought 'gosh, that doesn't look right'," said Mr Herman, 68.
The retired chartered accountant said that, during their "wrinkly gap year", the couple were constantly warned of dangers from theft of the vehicle to kidnap and worse, but faced no problems other than the need for a few minor repairs including a couple of punctures. "It was very nice reflection on human nature. The bad thing is when we got back I leave the car in Sainsbury's car park and find there is a large dent in the front wing," he said.
Mr Herdman, a retired chartered accountant, and his wife, 70, a retired lawyer, started their journey in July 2010 from Miami, driving up the east coast of North America to Halifax before crossing Canada and then heading south down the west coast.
After a couple of months in South America, they headed across to Australia before the car was shipped back via Turkey for the drive home through Europe.
The couple eventually returned to the UK in November. To celebrate the achievement, the Royal Automobile Club is to put the Bristol 405 on display at its Pall Mall clubhouse from 3 January.