The Liverpudlian comedian is preparing for his upcoming 'Week of Hell' 290-mile triathlon later this month.
He completed 26.2 miles in his hometown in 4 hours and 25 minutes in freezing rain earlier today (February 9).
"4 hours 25 - not bad for a first marathon and first lesson learnt - underpants tend to rub," he wrote on Twitter.
Bishop's 'Week of Hell' will consist of a 185-mile bike ride from the Eiffel Tower on February 27, followed by rowing across the Channel for the second leg of his adventure.
The 45-year-old will finally complete three marathons in just three days, finishing his week in Trafalgar Square on March 2.
Bishop is aiming to raise money for a vaccine to prevent five diseases - diphtheria, tetanus, whooping cough, hepatitis B and haemophilus - for 250,000 children in Africa, as well as helping those living tough lives across the UK.
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