To become a Beefeater at the Tower of London you have to have done at least 22 years military service.

(Beefeaters aka “Yeoman Warders” must have been senior non-commissioned officers in the Army, RAF or Royal Marines. It is thought that their nickname is derived from their historic position in the Royal Bodyguard, which let them eat all the beef they wanted from the King’s table.  In fact the French nickname for the English is “rosbif”, which refers to the English style of cooking beef “roast beef”.)