On the rare occasions when the Queen drops her famous reserve and bursts into fits of laughter, the Duke of Edinburgh is never usually far away.
Whatever the playful Prince said must have been hilarious as his wife was overcome by giggles.
The outbreak of mirth took place at the annual Braemar Highland Games – one of their favourite engagements.
Dating back nearly 200 years, the event features traditional dancing, hammer throwing, caber tossing and tug-o-war.
Accompanying the royals were David Cameron and his wife Samantha, who was country casual in a Paul Smith trouser suit.
The British Prime Minister is traditionally the guest of the monarch at Balmoral for one weekend in autumn every year.
In 2010, Mr Cameron was unable to attend because he was on paternity leave for baby Florence.