Prince Philip's sense of humour is as sharp as ever as he nears his centenary birthday. The Duke of Edinburgh—who's famous for his jokes and the occasional off-colour remark—was at it again when he stepped out on Tuesday for his first public engagement in over a year.

At the ceremony, Philip was honoured as he transferred the role of Colonel-in-Chief of The Rifles to Duchess Camilla. In photos, the 99-year-old royal and the regiment's Commandant and buglers were all smiles. But it turns out there was more to it than just smiling for the cameras. Here's the joke Philip made with the men.

Prince Philip's joke during his rare public outing

Daily Mail reported on Lance Corporal Streetin's account of the July 22 event with Prince Philip. Streetin, who plays in the regiment's Band of Bugles, said Philip asked him how long he'd been playing the instrument, to which he responded "10 years." After that, Streetin recalled: "He asked me if that was all I did, the bugling, and I told him that we were assault pioneers as well.

"He said 'obviously keeping up your fitness then?' and then kind of looked me up and down and I was thinking 'Are you trying to say I am fat?!' That's what we were laughing about. He's a very fit man himself for 99. Just incredible," Streetin explained.

Prince Philip is respected for his "character" and "banter"

Lance Corporal Streetin went on to describe the regiment's respect for Prince Philip — and his "banter," which on Tuesday came in the form of a fitness sight gag. "In my lifetime I don't think I will ever do anything like this again. I don't think the Colonel-in-Chief will change again in the time I'll be doing it. 

"So it's been a great honour to step in. Someone of [Philip's] character, his charisma, you can't go wrong. That's what we like, we are all banter. And that's what he is," he said of the Duke of Edinburgh.

Prince Philip takes part in transfer of the Colonel-in-Chief of The Rifles at Windsor castle.

During the short ceremony at the quadrangle of Windsor Castle, Philip was thanked for his 67 years of service to The Rifles and its antecedent regiments. Duchess Camilla now takes on his former role as Colonel-in-Chief, and received the new position separately on Tuesday at Highgrove House.

For the 99-year-old royal retiree, the July 22 event was a rare honour, during which social distancing guidelines were enforced. He and the Queen will also relocate to Balmoral Castle in August, after spending nearly four months in lockdown at Windsor Castle.

Prince Philip attends transfer ceremony at Windsor Castle, 22 July 2020.