BRITAIN'S biggest lottery prize winners have helped to change the life of a teenage boy who lost a leg to cancer after buying him a new prosthetic limb.

Colin and Chris Weir from Largs, Ayrshire, gave a five-figure donation to buy the leg for Kieran Maxwell, 13, from Heighington, near Darlington, who was diagnosed with Ewing's Sarcoma, a rare and aggressive form of cancer which affects fewer than 30 children a year, in 2010.

He had his left leg amputated below the knee last March, despite undergoing chemotherapy, and since losing the limb has been determined to remain active, carrying the Olympic Torch through Bishop Auckland last month.

However, his replacement limb was heavy and slowed him down, so his parents Nicola and Alistair decided to try to raise money to buy him a lighter model from the US.

Mr and Mrs Weir, who won £161 million in the EuroMillions a year ago, heard about his battle and bought the new leg for him.

Mrs Weir said: "When we heard about Kieran and his family's fantastic efforts to raise money for a new prosthetic leg, we had to help. It is a privilege to support him and, with this new leg, we hope he will continue to be determined to remain active and live life to the full, despite his cancer and amputation. We wish him well."

Kieran's mother said her son started "yelling and dancing" around when he heard about the donation.

Mrs Maxwell said: "He couldn't believe it. I am still pinching myself. What they have done for Kieran will be a drop in the ocean for them but for him it will change his life. He can go back to being a normal boy."

Kieran, who has a younger sister Alyssa, is currently on a Scout camp with friends.

One of them, Ewan Barr, had told his grandmother about Kieran's battle for a lighter leg.

She lives near the Weirs, although she does not know them, and contacted them about Kieran's plight.

After posting them a letter on the Monday, she received a call on the Thursday from the Weirs' assistant, offering them help.

Kieran's parents will continue to fundraise, but will now hand over proceeds to the Toma Fund, which helps children with cancer.