The Duke of Cambridge and Duchess of Cornwall have written to Second World War Army veteran Tom Moore, whose fundraising efforts have captured the heart of the nation.
Prince William also made an undisclosed donation to the 99-year-old's appeal, which has raised more than £20 million for the NHS, Kensington Palace said.
'Captain Tom' has been walking laps of his Bedfordshire garden and originally set himself the target of 100 which he completed on Thursday.
The veteran was given a guard of honour by soldiers from 1st Battalion of the Yorkshire Regiment as he completed his mission, saying he was happy to be "surrounded by the right sort of people".
Initially, Capt Tom hoped to raise £1,000 before his 100th birthday at the end of the month. However, he says he plans to carry on as donations continue to pour in.
It comes as hundreds of thousands of people have signed a petition for the veteran to be knighted.
The Prime Minister's spokesman said Boris Johnson will "certainly be looking at ways to recognise Tom's heroic efforts".
“From his military contributions to his support for NHS staff, Tom has demonstrated a lifetime of bravery and compassion," the spokesman added.
Originally from Keighley in West Yorkshire, Capt Tom trained as a civil engineer before enlisting in the Army during World War Two. He reached the rank of captain and served in India and Burma.
Speaking to BBC Breakfast, the Duke of Cambridge described the veteran as a "one-man fundraising machine".
"It's incredible...it's amazing," he said.
"He's a 99-year-old war vet, he's been around a long time, he knows everything and it's wonderful that everyone has been inspired by his story and his determination."
Cover image: Captain Tom Moore has raised millions of pounds for the NHS (Picture: @captaintommoore / Twitter).