“‘Let’s do something really big,’ I thought. I’d done an ironman before – with a name like mine it was pretty much obligatory – but next I wanted to do something that was logistically possible, but I didn’t think was athletically possible for me. That’s when I stumbled upon the Enduroman Arch to Arc ultra triathlon – an 87-mile run from London’s Marble Arch to the Dover coast, swim the English channel, followed by an 181-mile bike ride to the Arc de Triomphe in Paris.  The clock never stops from start to finish.

My big warm-up event was the London Football Run when I ran 70 miles to all 13 London football clubs

“I started training in May 2014 and, although I had a general training plan, I never thought further than three months ahead. So by the end of last summer I’d done a six-hour swim and close to a 50-mile run. Then, over winter, I got my swim speed up and my running form better. In spring, I combined the summer and winter training. My big warm-up event was the London Football Run when I ran 70 miles to all 13 London football clubs.

I’d been running for 11 hours so I was shattered, my feet were in agony and I could barely walk

“It was tough going but I got to the start line fit and healthy. I set off at 2pm on Friday 14 August and I was pretty excited, with the predictable smattering of nerves. Things started off well until around the 52-mile mark of the run at Charing in Kent – one of my lowest points. I’d been running for 11 hours so I was shattered, my feet were in agony and I could barely walk.

“I had a support car with me on the run and the bike ride driven by my dad and my twin sister Rosie. Also in the car was my friend Elliot (affectionately dubbed my road butler) who was responsible for my feeds and any problems we had, and Dan Earthquake (the Enduroman official) who was responsible for my safety and upholding the rules.

We had a survival sleeping bag in the car so I bed down at the side of the road

“At that point I was feeling horrendous. We had a survival sleeping bag in the car so I bed down at the side of the road. Ninety minutes later I changed my socks and shoes, continued on and felt in great shape. The next 35 miles were done in about five-and-a-half hours.

“I stopped every 45 minutes to have a stretch and take a feed (a 750ml drink of whey protein chocolate orange flavour and maltodextrin mixed with water), and the last five miles were a very painful walk. There were some blisters, but it was mainly pressure on my feet that was such agony, it really felt as though my bones were creaking.

I had a battered sausage and chips at around 45 miles and I had a lot of kettle chips

“Where we could, we topped up my feeds with hot food – I had a battered sausage and chips at around 45 miles and I had a lot of kettle chips – the salty fatiness went down well. Then at the end of the run – which took me 18hours 55mins in all – I smashed down two bags of Haribo, which made me feel quite ill, but at least I got the calories in.

“A lot of people get unstuck because they’re a little too precious with their calorie intake, so I took on the calories when I could. The second I finished the run I had the Haribo, got a cooked breakfast and went straight to sleep. Then I had a three-course meal – consisting of three main courses – before the swim.

I started at midnight so I swam through sunrise, which was fantastic

“The most painful part of the challenge was the run, but the most challenging was the swim. I started at midnight so I swam through sunrise, which was fantastic – I looked to my left and just saw the sunrise and the odd supertanker. There were loads of jellyfish but none seemed to be interested in me and they were actually quite beautiful. So for the first 10 hours of the swim, I was immensely happy; I was pleased with my progress and felt comfortable and warm. Zone3 kindly provided me with a wetsuit, which was great, I didn’t get a single rub.

For about three hours I was swimming  two miles from France and I effectively didn’t move

“After about 10 hours, I made the mistake of looking up at France and thought I must only be about five miles away, so I started powering away. What I didn’t realise was that the tide was pulling me south, so the second I got into the current off Cap Gris Nez it started to pull me around the coast. I wasn’t strong enough to swim through it, so for about three hours I was swimming about two miles from France and I effectively didn’t move. It was so frustrating and I started panicking.

“My left bicep and shoulder started to ache quite badly and all I could see in front of me was generic French coastline. I had a support boat with me, with Dan and my friend Hamish (my boat butler) on board, but the minute you touch it, it’s challenge over. So there’s no option to rest.

“Eventually, 15 hours after I’d started the swim, they laid the boat up in the shallows and shouted to me, ‘We’re there, just swim to the beach.’ Even then I still thought I was drifting and I was getting quite emotional, until my hand actually touched the sand at Tardinghen beach.

“The channel is a very weird swim. There are a lot of variables and the weather and the conditions change very quickly, but that’s why it’s so alluring. I’d been training in bad conditions with Coldwater Culture and Enduroman over the winter to prepare myself, and that was key.

The first 25 miles on the bike was all about getting to McDonalds – I just had to get there and eat some McNuggets

“The time allocated for transition two is 12 hours after you get out of the water and I almost missed it because I had a problem with my foot. I had to strap it up with ice because it was really swollen and in danger of getting infected. It was very painful and I thought if this gets worse it could be game over. So the first 25 miles on the bike was all about getting to McDonalds – no matter how bad it was, I just had to get there and eat some McNuggets, my first hot food in a day and a half. Eventually we got there at about 7am and it was closed. I almost had a bit of a toys out the pram moment, but just about held back.

“I was assured there was a patisserie about 30 miles further along, but when we got there that was shut as well. Fortunately by that point, 55 miles in, it was getting to proper daylight and my aches and pains were fading. I was still very stiff and sore, but there was a good tail wind, my Kinetic-One bike was purring away and it was turning into a nice day. At 105 miles, I finally got my McNuggets at the side of the road. I had 30 by the way – I wasn’t able to get to 40, probably should have stopped at 20.

“Eventually I reached Paris, Elliot joined me on his bike, and we rode up the Champs-Elysées to the Arc de Triomphe together, which was awesome. Except we were cycling over cobbles, and the vibrations really hurt. So what should have been the most glorious ride of my life was actually pretty chuffing painful!

This challenge only has about a 50% success rate

“On finally finishing, the overriding emotion was relief and joy. It wasn’t like instant goal-scoring joy, I just felt relieved, tired and satisfied. I completed it in 77hours 17mins, which was the third fastest time ever and, at 25, I was the youngest person to ever complete the challenge, which was amazing.

“I always knew there was a risk that I wouldn’t complete it – this challenge only has about a 50% success rate. But so many people were backing me, friends and family had come out at all hours of the day and night to support me along the way, and so my greatest incentive was a fear of failure.

“Eventually someone else will become the youngest and the third fastest, but Enduroman number 23 will never get taken away from me and that’s just starting to sink in.”

Read more about Freddie’s Enduroman Arch To Arc  ultra triathlon challenge on his blog. Freddie, whose father is a four-times cancer survivor, is raising money for Macmillan Cancer Support, you can make a donation via his Virgin Money Giving page.