While 5,000 other competitors were snug in dry and wetsuits, Jonathan Haran, of Wakefield, wore only the flimsy outfit for the gruelling Tough Guy 2010 challenge.

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Last Sunday's event in Staffordshire included an eight-mile run and swim in underground tunnels filled with freezing water.

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But the painful ordeal was worth it for Jonathan, 31, a manager for Leeds refurbishment specialist Peter Cox.

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He hopes to have raised up to £3,500 through sponsorship to help the fight against, and awareness of, the liver disease three-year-old son Luke is battling.

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Jonathan said: "I was virtually naked and was so cold I must have been close to hypothermia. It took about eight hours to get the feeling back in my hands and feet. There was three inches of ice on the lakes we had to get through.

"I have never been so cold in my life, it was shockingly painful, but definitely worth it. On the day I was thinking 'never again' but I plan to give it another go next year."

Luke was just five weeks old when he fell gravely ill with rare liver condition biliary atresia. Toxins built up in his liver because the passage to his intestines was blocked.

He underwent a life-saving operation at St James's Hospital in Leeds to remove his bile duct and intestine.

Luke, who has a brother Edward, four, has been on medication ever since and it is likely he will need a liver transplant before he reaches his 20th birthday.

Jonathan and wife Joanna, 29, of Leeds Road, Outwood, Wakefield, want to raise awareness of the condition.

They say GPs they dealt with were unaware of it. They also hope to raise funds for the Children's Liver Disease Foundation (CLDF).
To donate, go to www.justgiving. com/jonathan haran.