For 10 weeks they will spend every day together in a car while also attempting to navigate more than 18,000 miles round the globe.

The purpose of this potentially marriage-breaking mission is to set a world record for the most economical round-the-world drive. The Taylors will be waved off from London on Tuesday by Sir Ranulph Fiennes, the veteran explorer, and plan to circle the globe in 50 refuels or less in an unmodified VW Golf 1.6 FSI with a 50 litre (11 gallon) tank.

Officials will be monitoring the trip to see whether the couple qualify for travelling the greatest distance using the least amount of fuel, a new entry in the record books. To stand a chance of success they must travel a minimum of 18,000 miles — the shortest distance allowed under rules laid down by Guinness World Records.

The trip is sponsored by Shell, which is also providing their fuel, a new formula that is claimed to be up to 15% more efficient than other petrols. Called Nemo 6121, it is the prototype of a new fuel Shell plans to sell on its forecourts in Britain later this year.

The petrol will be added to the Golf’s tank from drums and the amount used calculated at every refuel. GPS tracking will be used to determine the distance covered. “Everything is being done to make it as accurate as possible,” says John, a 45-year-old former professional footballer from Hexham, Northumberland.

The couple, who have three children aged 18 to 24, have already set 80 world records for economical and speed- endurance driving, including the 24-hour world speed record for a seven-seater, a Chrysler Voyager, in which they travelled 2,674 miles at an average speed of 123.8mph.

But this is the first time they have attempted to circumnavigate the globe. “Something has always got in the way, a war broke out or something, just before we were due to set off,” says John. “This is the dream drive.”

The Taylors have a well-worn mantra for economical driving: drive smoothly, use high gears, make sure the engine is regularly tuned and serviced, check tyre pressures, keep weight down and windows closed, use air-conditioning sparingly, remove anything that can add drag, employ cruise control, avoid overrevving, excess speed and rush-hour traffic, plan trips to minimise idling or detours and — most important — avoid arguments. The pair will take turns driving.

“We’ve been on a lot of drives together, although 27 days is the longest so far,” says Helen, 50, a former office manager. “But I’m not worried. This is a great opportunity to spend some time together. We’ll have Queen and Barbra Streisand on the stereo and, as long as I get a nice cup of tea every day, we’ll just have fun.”

Forget fuel economy. The Taylors should offer marital motoring guidance. Is there a record for time spent in a car with a spouse without pointless bickering?

You can track the Taylors’ progress from Tuesday at www.fuelchallenge.com

The fast way round

The fastest trip round the world by car was made by Mohammed Salahuddin Choudhury and his wife Neena from Calcutta in 1991.

They drove 24,901 miles in 39 days and 20 hours, starting and finishing in Delhi. The record has since been “rested” by Guinness World Records for reasons of safety.