John Jenkins is marking his centenary with his family in his home city of Portsmouth.
Earlier this year, he received a standing ovation from the Queen and US President Donald Trump when he addressed heads of state during the D-Day 75 commemorations on Southsea Common.
Describing being the centre of attention, Mr Jenkins told the PA news agency: "I've never been a nervous sort of person when faced by people of a higher rank because they are only human beings the same as I am."
He said of his milestone: "Well frankly I don't feel any different, in fact I think to myself 'how did I get here? but there it is, time creeps up on you and before you know it you're in your 100th year, which is amazing really."
Explaining the secret to his longevity, Mr Jenkins, who was made an MBE for his role as a company sergeant major in the Territorial Army after the war, said: "I've always been a keen keep-fit chap, I always used to like PT at school, I became a physical training instructor in the Army, I also used to do a lot of amateur wrestling in my younger days so that kept me pretty fit."
Mr Jenkins, who said football is a "big part of his life", also keeps active through his role as boardroom steward at Portsmouth FC and as a volunteer at the D-Day Story museum.
After leaving school, he became a bellboy for the Cunard cruise line in 1933 before he attempted to join the Royal Navy but was turned down because of his eyesight.
He went on to join the Hampshire Regiment of the Army before moving to the Pioneer Corps , in which he served as a platoon sergeant during the Second World War and was awarded the Legion d'Honneur for his part in D-Day.
Mr Jenkins said: "It's something you never forget, I landed on Gold Beach, someone said to me 'what did it feel like?' and I said 'it was terrifying', it was the only word I could think of at the time."
His granddaughter, Alison Baynes, explained Mr Jenkins had also been involved in a secret mission to carry out a reconnaissance trip to the Normandy beaches ahead of the landings to take sand samples to select the appropriate landing sites.
She said: "He was told to keep it a secret so he hadn't told anyone about it, not even his wife."
Mr Jenkins went on to become a trolley bus driver after the war before working as a crane operator at Portsmouth Naval Base.
He was married to Peggy and has one daughter, two granddaughters, five great-grandchildren and a great-great-grandson.
Mr Jenkins became the oldest man to abseil down Portsmouth's Spinnaker Tower at the age of 95 in 2015, carried the Olympic torch in 2012, was awarded Portsmouth Volunteer of the Year in 2016 and National Museum and Heritage Volunteer of the Year 2019.
Mrs Baynes, from Lymington, Hampshire, said: "He's a remarkable man, it's hard to think of him as 100.
"He's a people person, fiercely independent and a real inspiration."