Prince William has made a private donation to Captain Tom Moore, as the 99-year-old hits more than £18m for NHS charities.
William and Kate wrote to Cpt Moore after he hit his target of completing 100 laps in his garden.
Speaking on the BBC, Prince William called the veteran an “absolute legend”.
He said: “It’s incredible, I did see it on the news the other night and I thought ‘Good on him’.
“It’s amazing and what I love also is that he’s a 99-year-old war vet who’s been around a long time, knows everything, and it’s wonderful that everyone kind of has been inspired by his story and his determination.”
William also called him a “one-man fundraising machine”.
When he was played the interview, Cpt Moore said: “Well that I think is absolutely amazing. That my super prince can say something like that.”
The contents of the letter from the Duke and Duchess of Cambridge have not been released.
The prince is likely to have praised the efforts of Cpt Moore, who has now said he will continue walking in his garden as long as people continue donating.
Kensington Palace confirmed the donation from William, 37, but did not disclose how much it was.
It comes as Boris Johnson confirmed he will look at ways to honour Cpt Moore, with an online petition calling for a knighthood reaching 485,000 signatures.
The Prime Minister’s spokesman told a Westminster briefing: “From his military contributions to his support for NHS staff, Tom has demonstrated a lifetime of bravery and compassion.
“The Prime Minister will certainly be looking at ways to recognise Tom’s heroic efforts.”
Originally from Keighley in West Yorkshire, Cpt Moore trained as a civil engineer before enlisting in the Army for the Second World War, rising to captain and serving in India and Burma.
Prince George’s godfather, the Duke of Westminster, made his own donations to NHS charities earlier this week, adding £10m to his previous donation of £2.5m.
Billionaire landowner Hugh Grosvenor said: “On behalf of my family and everyone at the Grosvenor Estate, I want to say a huge thank you to all our amazing NHS staff and everyone providing critical frontline services.”
He added: “We are all humbled and incredibly grateful that you are working tirelessly to keep us safe and keep the country functioning.
“NHS staff and key workers don’t work in isolation. They have children and families whose health and well-being will also be highly impacted by this crisis.
“As they keep us safe, I want to help provide as much support to them and their families as we can.”
A sum of £5 million will help create a Family Fund within NHS Charities Together, while £3 million will go to national medical research and development linked to the Covid-19 illness and £2 million to charities providing frontline support to those suffering the greatest long-term economic and social impact.