Which Car? magazine is urging consumers to stop but not shop at motorway service stations. The magazine surveyed 51 sites and bought a selection of snacks (500ml still water, 250ml can of Red Bull, 215g bag of Jelly

Babies, a large chicken salad sandwich and a 50g packet of Walkers or McCoys crisps) in each one.

The snacks cost just £5.48 at Sainsbury’s but much more at the motorway services, with five shops charging more than £10 for the items.

The What Car? staff found that bottled water had the highest mark-up - costing £1.89 at the Moto Southwaite site on the M6, for instance, and just 43p in Sainsbury’s.

It was not all bad news though, as the survey team found that motorway toilets were generally "impressively clean" and well-presented with some even displaying flowers.