From Wikipedia

Empire of the Seas
Episode One

Heart of oak

The Royal Navy of the United Kingdom is the oldest of HM Armed Forces (and is therefore known as the Senior Service). From the beginning of the 18th century until well into the 20th century it was the most powerful navy in the world, playing a key part in establishing the British Empire as the dominant world power from 1815 until the early 1940s. In World War II the Royal Navy operated almost 900 ships. During the Cold War it was transformed into a primarily anti-submarine force, hunting for Soviet submarines, mostly active in the GIUK gap. With the collapse of the Soviet Union, its role for the 21st century has returned to focus on global expeditionary operations.