The Duke of Cambridge has described Gareth Thomas as a "legend" after the former Wales rugby star revealed he is HIV positive.
Thomas, who came out as gay in 2009, is thought to be the first UK sportsman to go public about living with the virus, and has revealed he was driven to suicidal thoughts as a result of his diagnosis.
He went public with his illness after being put "through hell" by blackmailers who threatened to expose his secret, saying he hopes his openness will help end the stigma around the condition.
Thomas' decision to speak out has earned widespread praise and won the backing of the Duke of Cambridge, who is the patron of the Welsh Rugby Union.
Through his Kensington Palace account, adding "W" meaning it was written by William himself, he retweeted Thomas' video.
He added the message: "Courageous as ever – legend on the pitch and legend off it. You have our support Gareth. W"
Thomas, 45, became the first Wales player to win 100 caps for his country.
He won his 100th and final cap at the 2007 World Cup in France and scored 41 tries for Wales between 1995 and 2017. He is 13th on the all-time international test try-scoring list.
The Cardiff Blues player also won three caps for the British and Irish Lions, and captained them during the 2005 Test series in New Zealand, before ended his career in rugby league.
The coach of the current Wales rugby team Warren Gatland was asked about the Thomas news at the team's World Cup training camp in Kitakyushu, Japan.
"It's always sad when an ex-professional sportsman picks up an illness of any kind," he said.
"Our thoughts go out to him and we hope things are as good as they possibly can be.
"As the players become aware of the news, I'm sure they'll talk about it."
Last November, Thomas was attacked in Cardiff city centre in a homophobic hate crime, but asked South Wales Police to deal with the 16-year-old assailant by way of restorative justice.
The sportsman now takes one tablet containing four medications each day, and doctors have said his condition is under control to the point that it is considered "undetectable" and cannot be passed on.
Thomas said that his husband Stephen, who he met after his diagnosis and married three years ago, does not have HIV.
The Terrence Higgins Trust said Thomas' story will "transform attitudes towards HIV that are stuck in the 1980s".
The HIV charity said: "Gareth is proof that an HIV diagnosis shouldn't stop you from doing anything you want to do."
"Gareth blazed a trail by being the first rugby player to come out as gay and has done so much to encourage inclusion and diversity within the sport.
"Now he is doing that once again with HIV, showing that this virus doesn't need to be a barrier when you're diagnosed and accessing treatment."
Thomas, who took part in a 140-mile Ironman triathlon in Tenby hours after revealing he is HIV positive, told the Sunday Mirror: "I've been living with this secret for years.
"I've felt shame and keeping such a big secret has taken its toll.
"I was in a dark place, feeling suicidal. I thought about driving off a cliff.
"To me, wanting to die was just a natural thought and felt like the easier way out, but you have to confront things.
"I've been threatened by people who said they would give away my secret. It's sick and I've been through hell.
"I was being blackmailed and in my mind I thought you only get blackmailed for something really bad, which compounded the feeling of shame."
For confidential support call the Samaritans on 116123, or visit a local Samaritans branch.