A former Pride of Britain winner from Portishead has had to cut his latest challenge in the US short because of extreme weather conditions.
Ben Smith had previously completed 401 marathons in 401 days to raise thousands of pounds for charity.
The ultra-athlete aimed to run and cycle 10,700 miles across all 50 US states in 86 days to raise £104,000 for the 401 Foundation.
His journey ended on day four of the challenge because of the severity of the searing heat and tropical rainstorms.
Helen Lazenby, Operations Support at 401 HQ, said: "I have been speaking to Ben every day sometimes four or five times a day to keep a close eye on him.
"I could sense there was something wrong after he completed day three. He was exhausted.
"Ben decided to walk half marathons to save more time, but it still meant that he had to get up a 3.00am to start his day.
"It was his intention to cover any lost miles later in the Challenge when his leg had healed properly but to have lost the miles early on was not the best start for him and it started to play on his mind.
"He got up on day four and powered through yet another 86 miles. We spoke and I just knew it was the time to have a very difficult conversation with him."
Ben had travelled to the USA on June 12 – whilst suffering from an injury – and had already completed the equivalent miles of two back-to-back ironman events in days.
Shaun, 401 Foundation Chairman, said: "My priority is to keep Ben safe.
"The 401 Foundation is a mental health charity after all, and I could see he was not only struggling with the elements and the environment but being completely on his own was particularly hard for him.
"His steely determination to keep going is just incredible so to have to stop now will be devastating for him.
"He is probably the most selfless human I have ever met. All of his family, friends and supporters will know what an impact this will have on him.
"The focus now is to get Ben home and help him fully recover.
"We would like to thank all our sponsors and supporters; all their wonderful comments and show of support has not gone unnoticed and although Ben is devastated, we will get him through this difficult time in recovery."
The money raised for 401 Foundation will help to develop a mental wellbeing app.
Ben has previously raised money to increase awareness of mental health support charities as he was bullied as a teenager and tried to take his own life twice.
He also suffered a mini-stroke aged 29 following years of bullying and physical abuse at boarding school.
A friend encouraged him to join a running club during his recovery and he found it helped him regain mental and physical health.