HMY Britannia was the British royal yacht of Queen Elizabeth II, serving as a floating residence and diplomatic venue for over 44 years. Launched in 1953, the vessel traveled more than one million nautical miles across 135 countries before being decommissioned in 1997.
Commissioned on January 11, 1954, Britannia was the 83rd royal yacht since the restoration of the monarchy in 1660. During her career, she hosted 968 official voyages, serving as a venue for state visits, royal honeymoons, and family holidays, while also acting as a significant diplomatic tool for the United Kingdom. The ship was designed with three masts and carried a crew of 220 Royal Yachtsmen.
Today, Britannia is permanently berthed at Ocean Terminal in Leith, Edinburgh
 
Interesting facts...
Privacy is key: To prevent unwanted glimpses into the royal bedrooms, the windows to these suites were installed higher than those elsewhere on the ship. Additionally, the teak windbreak on the Royal Bridge was specifically designed to prevent sea breezes from lifting royal skirts during public appearances.