Jane Tomlinson has run a series of gruelling races

Mrs Tomlinson managed to complete the first two legs - a 4km swim and 120km bike ride - in 8hrs 35mins but was five minutes over the cut-off time and was disqualified.

It meant she was unable to finish the 30km run around Nice. Mrs Tomlinson smiled through her tears and said: "I've really enjoyed myself."

She said: "I'm not disappointed, because I really couldn't have tried any harder.

"I would normally have been disappointed but I've tried really hard today, I didn't think I'd even get out of the swim, and I'm just really pleased I managed to complete the 4km swim and the 120km bike ride."

'Beaten by the clock'

Ryan Bowd, a triathlete, who accompanied the 40-year-old from Rothwell, Leeds, around the course, said she had accomplished things that many healthy people could not.

"It's just a shame we got beaten by the clock and missed the cut-off point of the run by minutes.

"This is one of the toughest bike courses of the world. There were times when I thought she was going to give up, and times when I thought she really should give up, but she just keeps going."

Her husband Mike, 43, and son Steven, seven, ran to embrace her as she put down the bike.

"She's been beaten by the clock," he said. "She's well enough to do the run so we couldn't ask any more from her.

'Just astonishing'

"It was only three weeks since she had radiotherapy, I can't say the amount of admiration I've got from her, it's just astonishing.

Taking part in the competition was Ms Tomlinson's latest push towards her target of raising �1m for cancer charities.

Mrs Tomlinson vowed never to complete another challenge following her "Rome to Home" challenge in June, but decided to carry on to raise as much money as possible.

Mr Tomlinson said Jane's appeal had raised about �925,000 so far with about �7,000 coming in every week.