Shane Williams knows himself about rugby union's concussion risks after his glittering career at the highest level - and now Wales' all-time leading try scorer is aiming to help the sport become safer.
The former British and Irish Lions wing has filmed a documentary for BBC One Wales, 'Shane Williams: Rugby, Concussion and Me', in which he explores how the sport is taking steps to reduce head injuries and the damage they cause.
Williams speaks to leading medical experts as well as rugby players and coaches and, at one point, the 42-year-old himself is the subject of "scary" examinations to determine the potential effects of head injuries.
It is also a project with personal significance for the former Ospreys player, whose son Carter and daughter Georgie have started playing rugby.
'Not scaremongering parents'
Williams hopes the programme and its findings can ease the concerns of those who fear about rugby's concussion risks.
"It is an important issue for anyone, but I was a little bit worried about agreeing to do it at the start because I didn't want to be seen to be scaremongering mums and dads letting their children play rugby," says Williams.
"Then I thought, if I don't do it, someone may do it who is not as positive about rugby as I am.
"It's a great sport. It brings such values to youngsters and people and it's the best thing I've ever done.
"I have certainly been concussed in my career - I've been knocked out a few times, had a few bangs on the head, but knew so little about it.
"So to do this programme I spoke to professionals, experts, doctors, nurses and so on - that was the way forward for me. I'm glad I did it.
"I'm far more educated, which means my children are far more educated and hopefully the people around me will be more educated when they see the programme.
"It's very important. We need to look after our brains. It's as simple as that. Not just in rugby - it's all walks of life."
Williams admits undergoing tests to find potential signs of brain damage was "scary" initially, but he was glad to play an active role in the research, particularly as the results were positive.
"That was quite scary actually because we were able to identify to see if there were early signs of dementia or whether or not I had any effects from contact over the years," he says.
"Thankfully I was alright.
"It's to say, if you play rugby it does not mean you're going to have dementia or you are going to be concussed every time you play."
Making rugby safer for future generations
Williams' research takes him from the very top of the game with World Rugby, the sport's global governing body, down to junior and grassroots rugby, including his hometown amateur club, Amman United.
Williams' son Carter suffers a head injury during the filming of the documentary, which shows the head injury protocols which take place in junior matches.
"I know the risks you take when you do play rugby but you take those risks when you play football, cricket, basketball, whatever," he says.
"You take those risks as a youngster when you're crossing the road or climbing a tree - I know that.
"Rugby's a great sport. Yes it's physical but the powers at be are trying to make it safer. We're telling coaches and physios, even at junior and amateur level, 'This is what you need to do if you think a player has been injured'.
"You need to take them off the pitch to assess them if you think he or she has had a bang on the head.
"Georgie plays at school and my son plays at club level and district. When I watch him now I can tell him 'Look, don't tackle with your head on the wrong side, tackle like this because it's safer and you're not going to get a bang on the head'.
"If you get a bang on the head - and you don't need to be knocked out - you come to the side and either come to me or you go to the physio or the coach.
"I'd like to think we've made the game safer for my son and anyone playing the game.
"When people watch this, mums and dads who are a little bit worried about their children playing contact sport, they can go away and actually think World Rugby are making this game a lot safer.
"Hopefully they can think their boy or girl is safer now because they've seen this documentary. If that's what I get out of this, then job done."
'Shane Williams: Rugby, Concussion and Me was broadcast on BBC One Wales and is available on demand