There has been much solemnity and seriousness in the Queen's life - but as she reaches her 96th birthday, what has often been overlooked is her sense of humour.
"Laughing things off has been an important survival technique," says royal historian Robert Lacey.
The Queen's well-developed "sense of the absurd" has been a vital private outlet from such a highly choreographed public life, where she often has to remain straight-faced, he says.
"She obviously takes her job seriously - but at the same time, it doesn't stop her having a sense of the ridiculous," Mr Lacey says.
The Duke of Sussex, after last week's flying visit to the UK, singled out his grandmother's "great sense of humour" as her best quality.