Conventional text books will tell you the last time England was successfully invaded was 1066 AD when William the Conqueror landed at Pevensey (in Sussex) England and defeated Harold at Hastings. Since then a combination of the Sea, Weather and the Royal Navy (latter supported by the RAF) largely kept England safe from foreign invaders.
England has faced a number of invasion since then and some of them have even been successful. Every one knows of the destruction of the Invincible Armada (as the Spanish called it) in 1588. That invasion might have worked had Parama's men been equipped and ready to move when the ships arrived. The Royal Navy did relatively little damage to the Ships of the Armada during the advance up the channel. England got a Lucky break, poor coordination and bad weather stopped the Armada more than the Royal Navy
100 years latter there was a successful invasion of England. This invasion is deceptively called the Glorious revolution. William of Orange (William III) and his wife the Queen Marry invaded England with an army of Dutch soldiers. Now they had the acquiescence of the Parliament and the Royal Navy did not interfere. Louis XIV didn't know about the invasion in time to mobilize his own Fleet or to throw an army into Flanders. Louis XIV owned James II more or less lock stock and barrel so he wanted him on the English throw.
OK so the Key to invading England is clearly being named William! HA HA.
Through out the 18th Century the French certainly believe it was possible to invade England successfully.
They had a plan of the books in the War or Austrian Succession a surprise assault across the channel in 1740 before the Royal Navy could mobilize. That plan was scraped because France hoped Britain and Hanover would just stay out of the war(they didn't) They also had a plan to invade in 1745 but chose to focus on Flanders. Part of the plan remained and became the '45 Rising the last Jacobite Rebellion in Scotland. French troops form the Irish Brigades did take part. Had the French made a more concerted effort the History of England might have been very different.
This brings us to the Seven Years War. The French had plan to invade England in 1759 (my regiment Saintonge was one of those slated to take part) but a combination of factors stopped it before it really got going.
1) as Jonathan Dull points out in his excellent book French Navy and the Seven Years War the French navy's efforts in the war were crippled by the Death of thousands of trained sailors, dockyard workers and shipwrights in the first year of the War. The culprit was Typhus, if this scourge had not struck the fleet it would have been in better shape for the rest of the war.
2) plans called for support from the Swedish and Russian Army and Navy to draw English ships in to the North sea and idealy to land a second front in Scotland. This time the French chose not to play the Jacobite card in order to keep the Dutch from interfering.
3) the only French Fleet capable of covering the invasion was destroyed at the battle of Quiberon Bay. The French Admiral Conflans actually had good plan run back to to the bay for a line and force the English to approach then though the shallow water in a storm. The wind changed direction at the wrong time and the French Navy was forced to turn back and fight the English head on. The Royal Navy ships were better maned and had a superiority of 24 to 21.
To create a back ground for my Invasion of England those three factors need to be mitigated.
1) They Typhus epidemic never happened leaving the French better able to man the ships they had and better able to build new ships.
2) The Swedish and Russian Armies will have not place here but they do send thier fleet into the North Sea drawing ships away from Hawk.
3) At Quiberon Bay the French ships have more able seamen and gunners aboard (see point 1) and the sudden shift of wind doesn't occur. The French fleet still takes a pounding but so does the English and several of the English ships are dis-masted and founder or run aground in the shallow confined waters. The battle is a French Victory and enough of Conflans ships are in good shape to sail to Calais to cover the invasion barges across the channel.
Of course the Royal navy recovers quickly and the French army in England must win or die as the French fleet cannot possibly get this luckily twice!
Parliamentarian Generals in a Conference of War -
7 hours ago