Captain Tom Moore, who raised more than £29m for the NHS by walking laps of his garden, has been made an honorary colonel on his 100th birthday.
Chief of the General Staff General Sir Mark Carleton-Smith made the appointment, which has been approved by the Queen, in order to inspire the next generation of soldiers.
The Second World War veteran is celebrating his birthday at home with his family after a whirlwind few weeks.
His determination captured the public imagination and after completing 100 lengths he decided to continue.
A Battle of Britain Memorial Flight flypast of a Spitfire and a Hurricane has been organised by the RAF to mark the day.
Capt Moore has been overwhelmed with birthday messages, including more than 140,000 cards which are being opened at a special sorting office set up at his grandson's school.
Royal Mail has painted a postbox in Capt Moore's village NHS blue in tribute to his fundraising efforts.
The postbox, in Marston Moretaine in Bedfordshire, has been decorated with a golden balloon.
David Gold, of Royal Mail, said: "We wish Captain Thomas Moore a very happy 100th birthday.
"His achievements are truly phenomenal, and this is reflected in the affection shown for him across the world."
Bill Chandi, who has been Marston Moretaine's postmaster for 32 years, said: "This has been an incredible time – far, far busier than even Christmas, but I am very happy to help as Captain Tom is a remarkable man, a real role model."
Both the Prince of Wales and the Duchess of Cornwall have written to Capt Moore to congratulate him on his achievements.
In a video released by Clarence House, Camilla said of "wonderful" Capt Moore's fundraising efforts: "That sort of thing makes you proud to be British, doesn't it."
Capt Moore will not be leaving his house at all on Thursday and has asked that people stay at home and wish him a happy birthday from afar.
"It is quite extraordinary that I am turning 100," said Capt Moore.
"It is even more extraordinary that I am doing so with this many well-wishers and I am in awe at the response my walking has had.
"To everyone who has donated, sent birthday cards and messages, sincerely thank you.
"Please stay home, stay safe.
"Tomorrow Will Be A Good Day."
He plans to spend his special day at home with his daughter Hannah Ingram-Moore and her family, who he has been self-isolating with.
They will all celebrate privately and will be joined by his daughter Lucy and her family through the use of technology.
"We tip our cap to you, Captain Tom," a special dedication video voiced over by @JNesbittTV launched to thank @captaintommoore for his valiant fund raising efforts for the #Covid19 Urgent Appeal. 💙 pic.twitter.com/NdIrHE3EDf
— NHSCharitiesTogether (@NHSCharities) April 29, 2020
The veteran and his family have been inundated with offers of gifts for his birthday.
"I am very comfortable and have everything I need," said Capt Moore.
"Covid-19 has left so many without, so please donate to those in need. Thank you."
Virtual birthday cards can be shared on social media using #CardForTom.
Capt Moore has been honoured with a Royal Mail postmark, with all stamped post until Friday marked "Happy 100th Birthday Captain Thomas Moore NHS fundraising hero 30th April 2020."
He has also had a Great Western Railway (GWR) train named after him in honour of his charity achievements.