How did Prince Philip end up in this 500-year-old Da Vinci drawing?

This Leonardo Da Vinci drawing has led some eagle-eyed museum visitors to suggest this guy looks a lot like Prince Philip, which is particularly curious as the drawing is owned by his wife, Queen Elizabeth.

Called A Man Tricked by Gypsies, it's on display at a da Vinci exhibit at the Kelvingrove Art Gallery and Museum in Glasgow.

Of course, it's NOT actually the Duke of Edinburgh, because the painting's from the 15th century, and he's 97, not 597.