IT STARTED as a drunken prank at the pub – now Rory Gilmour is about to run his 100th marathon.

The 58-year-old from Great Coxwell near Faringdon has run through the Saharan desert, the streets of Seattle and the Himalayan mountains.

But this month he will mark his century a little closer to home: Abingdon Marathon on Sunday, October 23.

Unlike many marathon runners, Mr Gilmour, a cleaner at Faringdon Community College, does not usually run for charity: he does it purely for fun.

But he will use the special occasion next month to raise money for a cause close to his heart – Oxford's Helen and Douglas House children's hospice.

He said: "One of my friends went to Helen and Douglas House, and when I went to an open day there I was very impressed."

As for how he was feeling about the milestone marathon he said: "My mood seems to change from thinking 'this is fantastic' to going 'oh my gosh'.

"These days I just tend to take it for granted."

Born in London, the young Rory moved to Denchworth near Wantage when he was young and went to a boarding school in Salisbury.

By his own admission he was not a sporty schoolboy.

But after school he moved to London and somehow ended up getting a job at the Olympus sports shop in Oxford Street.

One evening, some workmates took him out to visit some of the local pubs on a night that would change his life.

He recalled: "I was going out with some friends pub crawling, I was slightly drunk and one of them said 'I've just found this piece of paper'.

"I signed it quite happily, then a few weeks later I got a letter saying I had been accepted on the London Marathon.

"I hated sports and did anything to avoid it at school, but I wanted to prove to my friends that I could actually do it, so I started training."

The training paid off and he completed the run in three hours and 45 minutes – not a record-breaking time, but not bad either.

He said: "I quite enjoyed it actually, I did all the training then I thought 'I quite enjoy running'."

In the 34 years since, he has run marathons in Swindon, Niger, New York, Nottingham, Greece, Amsterdam, Long Island, Winchester and Birmingham.

In 1999 he joined the epic Marathon des Sables – a six-day, 251km "ultramarathon" through the Sahara Desert in southern Morocco.

His favourite marathon, he said, had been through the deserts of Jordan because he loved the scenery.

He said: "It was basically just desert with a few sand dunes and once in a while we saw some roaming nomads, but we also went past the place where they filmed Laurence of Arabia, and the people were very nice."

His best-ever time so far is three hours and 15 minutes – his slowest is four hours and 45.

This month he is aiming to clock somewhere under four hours and 15.