John Bishop has set off on the first of three marathons on consecutive days, hours after completing a gruelling cross-Channel row.

The comedian said his body had been taped up to ease crippling muscle aches as he set off in front of well-wishers from Dover, Kent, as part of a “week of hell” for the BT Sport Relief Challenge.

John was averaging 10-minute miles for the first hour of his run and after taking an early tumble, but quickly regained his stride.

Sport Relief’s Twitter feed said he set off “at a fair old pace”, but he then had a “a stumble and fall”, adding: “He’s fine but needs to go easy, those legs have been though a lot.”

John battled sleep deprivation and became “delirious” during the 26-mile row across the English Channel on just one hour’s sleep, after earlier completing a 185-mile cycle ride.

With fellow rowers Davina McCall, Denise Lewis and Freddie Flintoff, he completed the row in seven hours, 45 minutes, almost two hours longer than expected.

On Wednesday, joined by Dave “Comedy Dave” Vitty from BBC Radio 1’s Chris Moyles Show, John, 45, said: “I have had a bit of sleep which has made a massive amount of difference.

“Yesterday was awful. I was lucky because of the people I was with. The other three were amazing. They just carried me through, but in the middle of the Channel I was just so tired.”

The Liverpudlian, who is expected to be joined on the marathon route by Dermot O’Leary on Wednesday, admitted he had underestimated how hard the challenges were going to be.

The aim is to raise enough money to vaccinate 250,000 children in Africa, as well as help with projects in the UK and the comedian hopes to make it to Trafalgar Square in London on Friday.

The celebrities’ efforts have already raised more than £400,000 for Sport Relief.