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.
More top news
Rugby star Sam Burgess has moved to Bath but it's not just about wearing the blue, black and white top but learning a whole new ball game.
Details have been published of improved safety on the M5 in Somerset, three years after one of the worst road accidents in living memory
The Bewick's swan is the rarest in the UK, and new figures released today show that the bird is sadly getting even rarer.