Combined, the Atlantic Ocean, English Channel, North and Irish Seas, are an effective moat around the United Kingdom and, for the sake of this post, Ireland. Successful invasions are few and far between.
William the Conqueror managed to do it in 1066. The French came again in 1215 after King John disregarded the Magna Carta.
During the Scottish Wars of Independence, the French joined their Scottish “friends” in 1385 and in 1388 tried to take the Channel Island of Jersey in 1338 but were ultimately driven out.
In 1588 the Spanish sent an armada. Most of its ships were sunk in the English Channel by the Royal Navy or wrecked by bad weather. Thinking they were safe, a succession of British Kings and the Parliament allowed the Royal Navy to wither. The country got a rude awakening when the Dutch fleet severely damaged an unprepared Royal Navy fleet at Medway in June 1667. It was a ship-to-ship battle, not raid. At the invitation British Protestant noblemen, a Dutch Army arrived to limit the power of King James II, a Catholic who fled to France.
Never again would the British government allow its navy to wither. In 1744 during the War of Austrian Succession, the French invasion fleet sailed from Brest headed for the south coast of England. Weather and the Royal Navy prevented the landing.
In 1759, early in the Seven Years War, the French attempted an invasion to put a Catholic king – James III – on the British throne. French losses in naval battles with the Royal Navy prevented the landing.
During the American Revolution, the French and Spanish planned to invade the Isle of Wight and then cross the bay to take the Royal Navy’s main base at Portsmouth in August 1779. While trying to decide to whether to take the Isle of Wight or land in Falmouth on the southeastern tip of England, the Royal Navy and the weather drove them off.
So, imagine the surprise and shock amongst member of the British parliament when they learned John Paul Jones – rebel, a native Scotsman and a bloody Catholic no less – disabled all Whitehaven’s (the town where Jones was born and raised) guns, burns shipping and slips off into the night.
Since Jones’ attack, there were only two more successful raids on English soil, both by the French. In February 1797, a group of French revolutionaries landed in Scotland and tried to rouse the Scots against King George III. The rebels were captured at the Battle of Fishguard a few weeks later.
The last came in 1798 when the French landed in Ireland to support its rebellion against the British. They, along with the rebels, were defeated and reinforcements kept away by the Royal Navy.
Both Napoleon and Hitler considered invading England before rejecting the idea. Neither wanted to take on the Royal Navy. The message here is that if one has long coastlines like we do, one needs a strong, well-led and equipped navy.