If you spot Jonathan Pearce pounding the streets on Brighton seafront or staggering around Ditchling Common be warned - do not approach him!

Autograph hunters and well-wisher are likely to be given short shrift by the Match of the Day commentator as he endures his own personal hell.

Pearce is currently training for the London Marathon and admits pulling on his running shoes for the first time in 27 years has been a horrible experience.

The 48-year-old from Hassocks decided to run the marathon after his niece Lily died of an incurable disease at just eight months old last April.

Battling his way back to fitness has been agony at times but Pearce says the memory of Lily is the one thing that keeps him going during those long, painful training runs.

Pearce, who worked for Southern Sound in Brighton in the early Eighties, said: "I injured my knee when I was 21 and hadn't done any proper training for 27 years until I began preparing for the marathon in September.

"When I went for my first run I came out of my house, ran 200 yards and had to stop because there was nothing in my legs. I've built up my mileage slowly since then and lost one and three-quarter stones but it's been a real struggle.

"I've hated training all my life so I loathe every step. I am not one of those who says they love being out in the fresh air, getting close to nature as I'm not enjoying it at all.

"I've been recognised a few times when I've been out running but I don't advise people to come too close as I'm not in the best of moods when I'm training.

"My biggest problem is the fact I've got a chronic knee problem. I have to take painkillers every day, ice my knees two or three times a day and have a cold bath after each training run but I am still in constant pain.

"It hurts all the time but it is particularly bad when I am running but I just grit my teeth and carry on. It is hard to motivate myself sometimes but I know I am doing it for a good cause.

"I just hope I don't let people down but I know that won't happen because I'm determined to get around even if I have to crawl the last mile."

Pearce is running the marathon with Lily's father Dave Merritt and together they hope to raise £13,000 to fund research into Mitochondrial Disease - a fatal metabolic disorder which was largely unheard of until recently.

He has found it tough fitting in his training schedule with his work for the BBC but has been boosted by the backing of Premier League stars and Match of the Day colleagues.

Pearce, who ran the Sussex Beacon Half Marathon last month, added: "When I first told the people at work I was going to run the marathon they said yeah right' and laughed it off but now they are all behind me.

"One of the pundits on Match of the Day has promised to give me £500 if I do it and a Chelsea player has sponsored me for £1,000 so my job has helped.

"I hope people who listen to my commentaries or remember me from my young days on Southern Sound might like to donate some money because it is a very worthy cause.

"Losing Lily was terrible but there are a lot of people out there who might have the disease and not know it because it has only recently been diagnosed.

"I am certainly not a runner in any sense of the word so for me to do this would take something extraordinary and hopefully the fact I am well-known will help raise awareness of Mitochondrial Disease."

- To sponsor Jonathan go to www.justgiving.com/jonathanpearce1 or to find out more about Mitchondrial Disease and how you can help raise money to tackle to condition go to www.thelilyfoundation.org.uk.

- Jonathan will be at a special fundraising day for The Lily Foundation at Brighton Racecourse along with Match of the Day pundits Lee Dixon and Mark Lawrenson on Friday, May 23.