Baby William brought joy to his parents during his short life.

Now his grieving father will run the London Marathon to thank the John Radcliffe Hospital in Oxford for giving him four-and-a-half months with his son.

The hospital’s neo-natal care unit treated baby William and allowed parents Steven and Emma Radley, who work at Oxford Brookes University, to enjoy days out as a family.

Mr Radley, 36, from Witney, plans to run the Marathon in April to raise funds for the unit.

He said: “If it was not for the doctors being there, on hand immediately when he was born, and the nurses, consultants and experts he would not have survived.

“They gave him a chance at life and I want to repay them.”

William was born by emergency caesarean two weeks premature, on May 8, 2011. Doctors had earlier discovered he had serious cardiac problems.

They later found he had significant trauma to his lungs and a build-up of fluid in his body, all of which would have shortened his life.

William spent almost his entire life in hospital, but his health was improving and he was set to be discharged when he suddenly died on September 20.

Mr Radley said: “His birth was a horrific experience.

“It became very clear, very quickly that the doctors were not happy with the condition he was in, and we did not really get to see him at first.

“I was able to see him for a couple of minutes, two hours after he was born. He was attached to a respirator and there were wires and IV lines going in.”

Mr Radley took time off work to be with his family and they were able to bring William home for short day visits.

He said: “One of our good days was going to the Battstock music festival together in September. We met friends and had a day out as a family. But it was always only a day and he had to go back to the hospital at night.

“At the time they were big days, but now he’s gone we realise just how important they were.”

The day before he died, Mr and Mrs Radley, 33, had been talking to doctors about taking William home full time.

Mr Radley said: “He had been improving significantly but then he caught what we thought was just a cold, but it just knocked him.

“It was completely out of the blue and it was devastating, for us and for our family.”

Mr and Mrs Radley, along with their friends and family, have been fundraising for the unit since William’s death and have so far raised more than £9,000.

To support Mr Radley, visit justgiving.com/runningfor babywilliam