A former York House School pupil and Olympic torchbearer returned to give an assembly about his inspiring life.
Tom Isaac, the co-founder of The Cure Parkinson's Trust, visited the Croxley Green school on Thursday to talk to the children about how he has lived with the disease since his 20s.
He has climbed the highest peaks in Great Britain, regularly plays tennis, has walked the entire coast of the UK, and run the London Marathon.
More recently he carried the Olympic flame in Welwyn Garden City in recognition of the £350,000 he has raised for charity.
Richard Kelly, from the school, said: "Tom Isaacs is a wonderful speaker, a gentleman of great tenacity and a real inspiration to us all at York House School.
"We are very proud of his incredible achievements."