Prince Harry played the trickster earlier when he joined adventurer Bear Grylls at the launch of a unique fundraising challenge for a leading forces' charity.
The royal jokingly tried to put off the celebrity daredevil taking part in a nerve wracking "zip wire" descent from the roof of the Imperial War Museum.
The London landmark was used to host the launch of the Soldiers Challenge which aims to raise funds for ABF The Soldiers' Charity which provides lifetime support to serving and retired soldiers and their families.
Those taking part will attempt to complete as many military-style physical events as possible from a list of 35 activities that include everything from an obstacle course in the Tower of London's moat to abseiling in the City.
The time allowed to tackle the challenges is just four hours before the teams have to return to base at the Royal Chelsea Hospital.
Grylls, chief scout of the Scout Association, was joined by around a dozen members of the organisation, and said despite his action man image he never got "immune" from doing stunts.
The adventurer was joined on his trip down the wire by the Tomas family from the New Forest - parents Simon and Nicky and their teenage sons Sam and Jamie - who have signed up to compete in the challenge being staged next March.