Shedding and raising pounds - Jones tackles longest run

Jones was inspired after seeing an image of himself when he was part of the Wales coaching staff in 2025, when he weighed in at 24st 7lb (156kg).

"When I was out in Japan with Wales last year, I remember the camera panning to me at the end of the tour and I was massive," said Jones.

"I thought I need to do something about this. I had a bit of gout, too."

Jones is typically dry and self-aware in his personal assessment.

"I've always been the type to look in the mirror and think I look like Arnold Schwarzenegger, when I'm actually far from that," he added.

"I'd go to the gym and do bits and bobs but my diet wasn't great and it was the old cliche of walking up the stairs being hard.

"I needed a challenge to change things."

Jones, who is running in aid of two charities, St David's Hospice Care and Prostate Cymru, has recently weighed in at 19st 7lb (124kg) which is close to his ideal playing numbers.

He admitted he had issues with his weight whilst playing, and recruited support from Wales chief Warren Gatland and fitness coach Craig White.

"When I was a player, I needed to be at a certain weight," said Jones,

"I told Gatland and Craig, 'give me a weight and I'll stick to it'. If I was at that weight, I could play well.

"I'd often crash diet as a player. If I had a bad weekend, I'd get back to my ideal weight before the next match.

"It was stupid. But I don't need to be crash-dieting for Six Nations matches or Lions tours now.

"I've got a slow plan. Drop it down slowly and training every day in one form or another."

Jones admits he needed to change his diet.

"Chocolate has always been my weakness," he said.

"I've got a sweet tooth. So I cut that out, as well as bread."

Jones started slowly as he adopted the "couch to 5k" approach.

"As soon as I started doing it, I saw the benefit of the process. It was fascinating to see and develop week-to-week," said Jones.

"I enjoyed that and started ticking off the little milestones. It is a brilliant process.

"The first run was a five-minute walk, then a 90-second run, and so on. You're not going straight in and doing it.

"Once you've got that 5k, it was a sense of achievement and you get that buzz after running."

He took to his new sporting endeavour so well he soon upgraded his ambition.

"After that, I was thinking of doing a 10k, but then I saw Cardiff was long enough in the distance that I could train for a half-marathon," he added.

‘Weirdly, I enjoyed the running part of training, so it appealed to me.”

Jones recently did a 17km training run, not something he did during his 16-year rugby career.

"It's definitely the longest I've run," said Jones, who with typical humour went on: "If you added up all the distances I've run in Test matches, it probably wouldn't be far off that anyway!"

Jones says Harlequins players and coaches have been supportive.

"The boys have been brilliant," he said.

"A few of them have sponsored me. Some haven't, but that's mostly the big earners.

"I think they're waiting to see me finish first and then the money might go up a fair bit."

The former prop also believes it is a positive for the players to see him making the effort.

"I'm putting myself in a place where it's uncomfortable.

"I'm asking them to stay in the fight and stay in shape when it gets painful, so it felt wrong if they couldn't see me do the same.

"I do have perspective. It'll be hard, but there's harder things to do.

"I always tell the boys here you're not working down a mine. My grandfather was a miner. What he did was hard.“

Jones has not targeted a specific time for the half-marathon.

"People keep asking what time I want to get, it's more about getting around for me," he explained.

"I reckon there'll be a few other 19-odd stoners knocking around the same time as me, so we'll have a little race.

"I'm competitive but I'm fully aware I'm not going to win and made peace with it."

He also has added motivation courtesy of one of the Harlequins players.

"Cadan Murley put into ChatGPT the other day to see what time I should run it in and said if I beat that time, he'll give me more money.

"I'm happy with the time it said because if I can do it under two hours and 30 minutes, he will double the amount."

Jones will be supported on the course by his wife Nicole and daughter Isla.

His father might also attend with Jones admitting he is "glad to see me get off the couch and doing a bit".

"I am a little nervous about it, but I'm buzzing," said Jones.

"I've had the race number from the organisation and it means things have got real. I looked at that and thought, 'What have I done?'

"I might go incognito in the race so no one can see how slow I'm going, maybe I'll put a balaclava or a daffodil hat on, so I don't get abused!

"But I've heard good things about the event and how people support you. I'm hoping the Welsh public will get me around the last few miles."

Jones also hopes he might continue his running career.

"I'd imagine I'll want to try another half-marathon somewhere else after it," said Jones.

"But let's see how this one goes first before I start thinking about running across the Sahara Desert and world marathons and all that."