Matthew Disney, 38, took on his version of the fell runners' top test, the Bob Graham Round - climbing 42 Wainwright fells in the Lake District - but this time completely barefoot.
The former Afghanistan veteran started off in Keswick, bare-footing it up Skiddaw, at 931m the sixth highest mountain in England, before marching on to Helvellyn, then England's highest, Skafell Pike at 978m, then back to Keswick, climbing all the big fells in between.
Matthew, who has completed challenges such as climbing the highest mountains in the UK carrying a rowing machine on his shoulders and then rowing the distance walked on top, said this was the hardest challenge he has taken on.
He was supporting Rock2Recovery, a charity that helps all soldiers, serving and veterans, that suffer post traumatic stress disorder and The Royal Marines Charity, which helps both serving service people and veterans and their families in hard times.
He said: "It was the most brutal challenge I have done and definitely the most painful.
"I had warmed up by doing four peaks barefoot last year and I thought I needed to take it to the next step.
"I had heard of the Bob Graham Round, which many fell-runners regard as the ultimate challenge, 42 peaks in 24 hours, and wanted to do a version of that but barefoot.
"Barefoot walking and running has become quite popular in recent years, its very natural. But this was not just one step up, it was about six or ten times harder!
"The third stage was the hardest, Bowfell to Skafell Pike. Absolutely brutal. I was to meet my partner, Lauren Lancaster, there for mental and moral support, but it was so hard and I arrived in the dark. I was not comfortable doing the the trek from Skafell Pike to Skafell at that time so, I had to add on a day to the challenge.
"I ended up doing it in 33 hours. It was 66 miles and I climbed the equivalent height of Everest overall in the end.
"It was certainly unique. Knowing that I am the only person to have done it barefoot is fantastic, but in reality there is a very good reason why no-one else had done it!
"On that third leg, I was asking myself why did I think of doing this barefoot, but being a Royal Marine, you are a little bit stubborn, so you don't ever want to give up."
Luckily the only damage done during the whole bare-foot epic was a barbed wire fence scratch on his arm and a couple of thistle prickles to his foot.
It is the latest in a series of challenges Matthew has taken on. He climbed the height of Everest at Bloomfield Road stadium on a stair-climb training machine in 2019 to raise money for forces charities and during lockdown he built a mini-mountain in his partner Lauren's garden in Penwortham, to climb the equivalent of the highest mountain in the solar system to support the NHS.