LONDON - Already Britain's oldest employee, 101-year-old Buster Martin now aims to become the world's oldest marathon runner by completing the London Marathon and celebrating with a pint of beer and a cigarette.

Sprightly and bearded, he completed a half marathon at the weekend in five hours 13 minutes. The former Army physical training instructor works three days a week for a London plumbing firm and says he has trained for the April 13th race in his spare time.

"I've said I'll attempt it," he told Reuters by telephone from his workplace at Pimlico Plumbers. "I haven't said I'll complete it. If I do make it, all the better. I hadn't thought of doing it before but someone asked me and the money goes to charity so why not?"

His sponsorship money will go to the Rhys Daniels Trust, which provides temporary accommodation for families of patients in specialist children's hospitals.

Martin, who had 17 children and returned to work at the age of 99 saying he was bored after two years of retirement, would beat the previous record for world's oldest marathon runner by eight years.

"If I finish, I'll do what I always do and have a pint and a fag," he said. "People ask what is my secret but I haven't got one. They say fags and booze are bad for you -- but I'm still here, aren't I?"