Rollercoaster fanatic Mark Lewis is aiming to spend 40 hours on one of the UK’s most iconic wooden coasters to raise money for Great Ormond Street Hospital.

Mark, who lives in Ebbw Vale and is a member of both the Roller Coaster Club for Great Britain and the European Roller Coaster Club, will attempt the challenge on the Megafobia ride at Oakwood Theme Park in Pembrokeshire.

The ride was voted the best wooden rollercoaster in the UK at the Golden Ticket Awards and, in 2010, it was listed as one of the Top 10 rides in the world.

Mark’s challenge will take place over a five day period from July 14th to 18th and will entail spending up to 10 hours at a time on the coaster.

It is not the first time the part-time DJ has ridden Megafobia for charity.

In 1996, he raised £1,100 for the children’s ward at Nevill Hall Hospital, and in 2010 he rode the attraction for seven hours to raise £1,200 for the Golden Grove Mansion Appeal.

This time the 44-year-old, who works at Llanarth Court Hospital, is hoping to raise more than £1,000 for Great Ormond Street Hospital in London.

The charity is close to Mark’s heart as his son Ryan, who is now 18, was born with a rare blood disorder and was treated at the hospital when he was just three months old.

“On my previous rideathons, all I could think about was when my little boy was in hospital. That is the main reason why I am doing it,” he said.

“When Ryan was in hospital, I stood in a lift and we were worried sick about our child at the time.

"But there was a little baby in the lift with a cleft palate who was very ill. I just thought, imagine what that young child and the family is going through.

“Despite what our child was going through, there were always going to be children much worse. That’s what has pushed me on to be honest, it is completely worth it,” he added.

Great Ormond Street Hospital is one of the world’s leading children’s hospitals with the broadest range of dedicated, children’s healthcare specialists under one roof in the UK.

The hospital’s pioneering research and treatment gives hope to children who are suffering from the rarest, most complex and often life-threatening conditions, from across the country and abroad.