20 Jul 2026
A former professional rugby player will be visiting Harpenden this week as he attempts a world-record-breaking endurance challenge by completing 100 ultramarathons in 100 consecutive days.
David ‘Jacko’ Jackson, who lives in north west Wales, hopes to raise £1 million for brain injury charities Headway UK and Head for Change with his challenge, titled ‘Mission IN-possible’.
Since starting out on May 29, Jacko has completed an ultramarathon – 50km – every day, and will be based at Harpenden’s Highfield Oval throughout the week.
The attempt is expected to break the current men’s world record for consecutive ultra-marathons, which currently sits at 80 days, but for Jacko, this challenge is about more than records.
In 2013, his professional rugby career was abruptly ended by a traumatic brain injury.
David Jackson was Nottingham Rugby’s most capped player and all-time top scorer, amassing 316 appearances and scoring 102 tries.
The road to recovery was uncertain, and at times, normal life felt impossible.
A huge part of Jacko’s recovery involved running and breathwork, tools that helped him rebuild both body and mind. But he is acutely aware that not everyone affected by brain injury has the same access to recovery, rehabilitation, or long-term support.
“Everyone thinks this challenge is impossible,” he said.
“But I believe in IN-possible. That belief runs deep – and it’s something my recovery taught me.
“I’ve experienced first-hand what recovery can look like – and I’ve also seen what happens when people don’t get that chance.
“That’s why this challenge is for Headway UK and Head for Change – and for the people whose lives are changed forever by brain injury.”
It took seven years after his brain injury for Jacko, who now works as a breath coach with his company Pro Breathwork, to run his first-ever marathon.
He wants as many people as possible to join in his ultramarathon challenge, spending four days at 25 locations throughout the UK, completing the daily distance through 5km and 10km loops.
The loop format allows anyone – runners, walkers, first-timers or experienced athletes – to join him, whether for 5km or further, and take on their own version of the ‘IN-possible’.
Having recently covered a total of 200km over four days in Northampton, Jacko will be in Harpenden from Monday to Thursday.
Jacko said: “This isn’t just about supporting from the sidelines. It’s about being involved; running your own IN-possible.
“Whether it’s your first 5km or something much bigger – this is about believing in yourself again. And drawing on the support of each other, as I’ve experienced strength is multiplied when shared.”
Fundraising manager at Headway UK Helen Craig said: “Jacko has firsthand experience of the challenges that come from living with a brain injury. His determination to turn such a difficult period of his life into something so positive is truly inspiring.
“We’re incredibly grateful to Jacko for taking on this extraordinary challenge. His efforts will help us to continue supporting people rebuilding their lives after brain injury, as well as raise crucial awareness of the reality of brain injury, all while bringing communities together across the UK.
“Everyone at Headway UK is incredibly proud of Jacko, who we’ll be cheering on every step of the way!”
Alix Popham, founder of Head for Change, said: “This is an unbelievable challenge, and full credit to Jacko for taking it on.
“Both charities are here to support people affected by brain injury, and that’s what it’s all about.
“We’re really looking forward to joining him for the final couple of days around Newport alongside friends and family.
“Wishing him the very best of luck as he completes this incredible journey.”
Follow Jacko’s ‘Mission IN-possible’ on Instagram at @thebreathrunningcoach
Donate to the challenge at: https://givestar.io/gs/mission-in-possible-2-marathons-a-day-for-100-days
