A BBC Wales documentary Gareth Thomas: HIV And Me to be broadcast tonight across the UK, follows the Welsh rugby legend as he comes to terms with his HIV diagnosis and his decision to take on the world’s toughest Iron Man challenge - which meant learning to swim in five months.

In the documentary, Gareth explains his reasons for taking on the challenge: “The stereotype of someone with HIV is they are weak, fragile, frail, I am none of those things. I want to prove that people with this condition can take on extreme physical challenges. So I’m giving myself 6 months to train to do an Iron Man. Two-and-a-half mile swim, followed by a 112 mile cycle ride.”

“With the right amount of training I can cycle 100 miles. And run a marathon. But swim two and a half miles? In the sea? We’ll I can’t swim. Water terrifies me so I’ve never learned.”

With the help of family, friends, medical experts and others with HIV, cameras follow him as sets about tackling the stigmas, myths and misunderstandings surrounding the condition. Modern medicine may have made the virus treatable and non-transmittable but old ideas about HIV still persist and Gareth is on a mission to smash the stereotypes.

The documentary will also show the moment Gareth reveals his diagnosis to his friend and fellow Welsh rugby star Shane Williams for the first time.

Shane Williams responds to Gareth’s revelation: “It’s not something I was expecting Alf, I’ve got to be honest.

“But my concern is that you’re OK... As far as I’m concerned it doesn’t affect anything - as long as you feel that - then nothing changes pal. I’m glad you’ve told me - I feel honoured.”