He has won every major tennis tournament in Scotland, beaten Wimbledon champion Pat Cash, represented Great Britain at the World Championships - but you won't hear of Malcolm Watt's achievements from the man himself.
At the age of 42 he was diagnosed with frontal lobe dementia. Four years later, he struggles to speak and needs round-the-clock care.
Put him back on a tennis court, however, and a dramatic transformation takes place.
He may not be able to keep track of the score but, for his age, he remains one of the best players in Scotland.
For his family who now care for him in Helensburgh, the game offers an enduring connection with the talented son they remember from his youth.
And for doctors, it's a tangible demonstration of the role exercise can play in alleviating and managing the symptoms of dementia.
Malcolm's condition, also known as frontotemporal dementia attacks the areas of the brain associated with language, decision-making and emotion.
His father Tommy recalls when he first realised something was wrong.
"On occasion, when I would speak to him on the telephone, he would veer off the conversation and talk about something entirely different," he said.
"I just didn't understand it. It didn't cross my mind that it would develop into what it has proven to be."
Unlike other forms of dementia, his condition tends not to affect visuospatial skills. In terms of power, accuracy and physical fitness, he still plays at the level of a semi-professional.
On court, his hitting partner Ian Campbell says another change comes over Malcolm, giving his friends a glimpse of the man they knew before.
"When we're standing off the court, he's often agitated and not too sure of his environment, but as soon as we start hitting a ball, he seems to calm down. He looks happy. He's just Malky. He's exactly the way he was when he was competing.
"Malky was always pretty funny - and the humour's still there. He still gets annoyed on the court, as he did. He still goes a bit crazy at times. So there's large parts of his personality that I can still see as him."
Malcolm's talent for tennis was apparent from an early age. He was winning tournaments when he was 12, won a tennis bursary to Stirling University and as a teenager was Scotland's number one and number four in Britain.
Twenty five years ago he beat former Wimbledon champion Pat Cash at a tournament in France.
"He entered the normal tournament in Scotland and he won them all with ease," says his father. "So he went down south where he won a lot of tournaments. He was good enough to go on a professional tour in Europe."
Later he became coach at Newlands Lawn Tennis Club in Glasgow.
Many of those skills on the court appear to be hardwired into his brain, surviving the onslaught of dementia.
Doctors and other experts are watching the progression of his illness with interest - especially the impact of the regular knockabouts on court.
Prof June Andrews, director of the Dementia Centre at the University of Stirling believes exercise can help in different ways.
"The fuel for your brain is oxygen," she says. "The more exercise you do, the more oxygen you are bringing into the brain.
"Even if the brain is already a bit damaged by dementia, that exercise brings more oxygen and can help your brain to function better.
"The second thing that seems to make a difference is that exercise has a really positive effect on your morale, makes you feel better.
"The most difficult part about dementia is stress, so anything that reduces stress makes the person better. So for someone like Malcolm, stepping onto a tennis court - he knows where he his, he knows what he has to do. That's really important for him."
Malcolm Watt may not be the man he used to be. His dementia has cost him dearly. But on court at least, he can still give his friends the run around.