Sean Billington was devastated when his close friend died suddenly.

Mark Hudson was only 33 when he had a heart attack in his sleep and never woke up.

Determined to do something, Mr Billington will leave Bermuda in March and spend three months walking 1,172 miles across Britain with a 40lb rucksack as a fundraiser for Cardiac Risk in the Young, in Mr Hudson’s memory.

He hopes to present the UK charity with £11,720 at the end of his trek from Land’s End in England to John o’Groats in Scotland. Mr Billington is promoting his cause on Instagram and Just Giving.

“The charity that I'm doing it for is very, very close to my heart,” he said. “My very, very close friend died. He went to sleep one night and simply didn't wake up. He wasn't the first friend of mine for that to happen. As such, it makes perfect sense to raise money for Cardiac Risk in the Young.

“It's been on my bucket list for years but I never really had the opportunity to do it until now.”

At least 12 “apparently fit and healthy young people” die in the UK every week. According to Mr Billington, CRY works with cardiologists and family doctors to “establish good practice and appropriate screening facilities” for young people.

It is an issue that is now topical. Buffalo Bills player Damar Hamlin suffered a cardiac arrest during an NFL game last week.

“Not only is it a gigantic challenge and one that I'm personally excited about, it's also for a great cause,” Mr Billington said. “For many, many years, it was always on my list. It was always more a case of ‘when’ rather than ‘if’.”

Laden with a rucksack and walking poles, the accountant does practice walks along the Railway Trail and Elbow Beach – about 60 miles a week.

“I'd love to be able to swap Bermuda's humidity for a few more hills and mountains,” he laughed. “It was hard going when I first started but now it's feeling good.”

The majority of people tackle the journey by bike and complete it in roughly a fortnight. Mr Billington will be one of the “very few” to walk it.

The Land’s End to John o’Groats Association will track his progress and present him with a certificate on completion.

“While hundreds, perhaps thousands of people cycle it each year, very few people walk it. No one knows the exact number but I can't imagine it being more than about 50 to 100.

“There’s no official route. Most people select their route based on their own interests. For me, I wanted to walk the Pennine Way but avoid coastal paths. To obtain the certificate from the Land’s End to John o’Groats Association, the key thing is to register your walk and obtain evidence throughout by getting your form stamped in post offices along the way.”

He had to decide early on whether to walk from Cornwall to Scotland or the other way around.

Mr Billington considered his start date and decided to begin in the south and head north.

“As I'm starting in March, south to north is most logical as the weather will remain more consistent. I’ll also slightly benefit from the prevailing wind which blows south to north and have the sun behind me for most of the day. I won’t escape the rain though, so I've got good waterproofs.”

His wife, Gillian McCann, will join him at various points along the route; friends have also promised to keep him company.

“While I'll be doing it on my own from start to finish, the support and interest that I've received from so many people – friends, family and other acquaintances – has been amazing. Lots of them are planning to visit me, and even more are planning to join me for a few days, hiking along the way.”

Mr Billington has booked his hotel accommodation along the route but his big concern is not making it to every pitstop on time.

“Booking all the accommodation in advance is high risk. My biggest fears are blisters, muscle strains, of getting ill, which would cause me to be delayed and not reach my accommodation. However, in general, I’m walking six out of seven days so at least I’ve got a spare day to catch up if needed.”

Most appealing about the trek is that it will allow him to eat whatever he wants every day.

“I'm looking forward to actually getting stuck into the walk because it basically means I can eat exactly what I fancy because I'm going to be burning an extra 2,000 to 3,000 calories per day,” he said. “So it’ll be the great big fried breakfasts in the morning and lots of chocolate bars

“I've set a challenge to make sure I try every type of chocolate bar available in the UK.”

His wife, his parents and Mr Hudson’s parents will all be waiting for him in John o’Groats. How they will celebrate the accomplishment is anybody’s guess.

“John o’Groats is an absolute nightmare to get to,” Mr Billington said. “Other than a hotel, there's nothing there. Once we get back to where we are from in England, we may well organise something.”

• For more information on Sean Billington’s fundraiser follow him on Instagram @a.great.british.walk or visit bit.ly/3GsACgK