The Duke of Edinburgh couldn't resist one of his famously cheeky quips when he accompanied the Pope to Edinburgh's Palace of Holyrood on Thursday.
Many MSPs had donned tartan ties to mark the first state visit by a Pontiff to Britain.
Noticing that the Scottish Tory leader Annabel Goldie (pictured) wasn't wearing the tie, Prince Philip asked if she had tartan underwear on.
He joked: "Have you got a pair of knickers made out of this?"
Miss Goldie, known for her own witty ripostes, responded: "I couldn't possibly comment.
"And if I had, I couldn't possibly exhibit them."
Later the 60-year-old travelled to a spectacular open air mass, at which Susan Boyle had been invited to sing.
Other politicians reported the Tory leader as being in fits of laughter over her royal encounter.
She was heard to comment afterwards: "It's marvellous that humour is alive and well in the Royal Family".