He swam 2.4 miles, cycled a further 112 and, if that wasn’t enough, capped off the race in strength-sapping heat with a punishing marathon run of 26.2 miles.

Now, following the successful completion of one of the world’s toughest events, Canotec sales director Ian Smith is on course to raise £3,000 for charity in memory of his mother.

The New Forest endurance triathlete completed the Ironman Lanzarote 2010 in a respectable 12:33 hours as the mercury hit 30 degrees Celsius – finishing 620^th out of a field of 1,379 starters.

Dozens of friends, colleagues and clients pledged money after Ian dedicated race fundraising to the Alzheimer’s Society in memory of his 76-year-old mother Shelia, who was from Fawley.

Ian, 48, from Lymington, said: “I’ve been staggered by the generosity of people and my hope is that a cure is one day found to prevent or stall the corrosive memory loss that robs so many sufferers of their dignity and personal history.”

He added: “Our lives are filled with many challenges, however many others people’s lives are filled with far worse challenges than ours, so don’t hang about – if there is something you can do to help others, give a little time, sweat or money to support them.”

The Ironman Lanzarote is one of the most revered endurance races in the world and covers 140.6 miles of hilly terrain - equivalent to setting off at Fawley and ending up in Cardiff.

Ian, who burnt up 6,000 calories and drank 11.5 litres of fluid, said: “The race was a great experience and I settled an old score with life during it.

“The sea swim was my fastest ever at just over an hour, and the bike ride took just under 6:37 hours, but the run left me in agony at times, even though I felt strong, because of periodic cramp in the legs. 

“I completed the last stage in 4:37 hours, which was well below my expectation when measured against my normal marathon times. I now have unfinished business with this race, so I’ll be back.”