Bishop's Week of Hell will see the Liverpudlian travel 290 punishing miles from Paris to London. After completing the first stage on bike, he will row the channel from Calais to Dover. Upon arriving in England, Bishop will then run three marathons, which will see him arrive back in London on Friday (March 2).
Kicking off the challenge in Paris this morning, Bishop said that it felt "a bit like I am in a Mission Impossible movie with the Eiffel Tower behind me. I just need to get my head down and get a few miles under my belt."
However, just an hour into his journey, he fell off his bike on the outskirts of the French capital, after struggling to get his feet out of the cleats as he approached a busy set of traffic lights.
Wasting no time, Bishop - who is already suffering a sore neck, a bad shoulder and a painful left hamstring - was back on his bike, and completed 55 miles before stopping for a break. He commented: "It's lunchtime and I've done 55 miles - which on any other day in my life would be amazing, but today there's still 130 odd miles left to do.
"I'm trying not to think about the row tomorrow - and as for the Marathons, it's probably best not to worry about them at all at this stage."
Various famous faces will provide support to Bishop along the way, including Dermot O'Leary, Davina McCall, Freddie Flintoff, Denise Lewis, Frank Skinner and Robbie Savage.
Bishop's Week of Hell will be the subject of a BBC documentary, broadcast ahead of Sport Relief weekend, which takes place from March 23 to March 25.
> John Bishop Sport Relief triathlon back on after French rowing ban
> John Bishop completes first marathon for Sport Relief training
See pictures of John Bishop setting off on his 'Week of Hell' challenge below: