Royal Yacht Britannia

HMY Britannia was built at the shipyard of John Brown & Co. Ltd in Clydebank, West Dunbartonshire, UK, being launched by Her Majesty Queen Elizabeth II on 16 April 1953 and commissioned on 11 January 1954.
The ship was designed with three masts, a 133-foot (41 m) foremast, a 139-foot (42 m) mainmast, and a 118-foot (36 m) mizzenmast. The top 20 feet (6.1 m) of the foremast and mainmast were hinged, to allow the ship to pass under bridges.
Britannia was designed to be converted into a hospital ship in time of war,[1][2] although this capability was never used. In the event of nuclear war it was intended that the Queen would take refuge aboard Britannia in the North West coast of Scotland.