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
13-year-old Hamish Anderson has been stopping at a Bristol cafe on his way to school to buy bacon sandwiches for two homeless men he passes.
17-year-old Katie Swan is making her debut in the main draw at Wimbledon today.
It's a good if fresh morning to get up to but that won't last - this afternoon the cloud builds up and outbreaks of heavy rain will follow.