Gary Barlow, Chris Evans, James May and Brian Cox have set off from Lands End in a pink Rolls Royce raising money for Breast Cancer Care.
The challenge will see them driving from Land's End to John O'Groats in a bespoke pink Rolls Royce Ghost.
They want to try and raise £1 million in 24 hours.
The four celebrities will stop off in Bristol as part of their trip.
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Cornish Kern, made by the UK’s Lynher Dairies Cheese Company, has been crowned World Champion Cheese at the World Cheese Awards.
Starting cloudy. Rain will move in mid-afternoon hitting the North Cornwall/North Devon coast first. Stronger winds but very mild at 14 C
Starting cloudy with rain moving in mid-afternoon. West Somerset turning wet first. Made more unpleasant by stronger winds. Highs of 14 C