A local consultant will take part in the Deca-Ironman challenge to raise money for Artificial Intelligence (AI) Radiotherapy Planning Software.
Stuart Gillett, from Murhill, Somerset, will take part in the race in Mexico starting on 24 September.
The challenge comprises of a 24-mile (38.6 km) swim, a 1,129-mile (1,802 km) cycle and a 262-mile (421km) run.
Mr Gillett, who is a head-and-neck surgeon at the Royal United Hospitals (RUH) in Bath hopes to raise £10,000.
He is fundraising in conjunction with RUH's trust charity RUHX to buy computer radiotherapy AI software for the new RUH Dyson cancer centre.
The RUH Bath NHS Foundation Trust says the software will provide cutting-edge radiotherapy planning to benefit cancer patients by freeing up consultant oncologists to concentrate on face-to-face care.
Image source, Stuart GillettImage caption, Mr Gillett wakes up at 4am to start his training before work
A Deca Ironman is ten continuous ironman races – ten times the standard iron man distance.
Mr Gillett, 48, who is already the current UK record holder for 3x and 5x Ironman distance triathlon said he has been waking up at 04:00 BST to train before work.
"I use my commute to complete most of my training. I will either run or cycle to work, or swim during my lunchbreak.
"At the weekends, I try and do longer runs and cycles," he added.
Image source, Stuart GillettImage caption, Mr Gillett says he has done long-distance runs in the Sahara, the Himalayas and the Arctic.
Mr Gillett is an ears, nose and throat consultant and a head-and-neck-cancer surgeon. He previously completed the Quintuple Ironman in 75 hours, 15 minutes and 22 seconds.
He came third overall and broke the previous British record by over 24 hours.
Mr Gillett said: "The human body can do far more than we give it credit for. It's only when you start pushing yourself you realise actually what you can achieve."
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