The low-lying beaches covering much of the Sussex coast have proved a temptation to many a foreign power wishing to conquer England.

So it proved when William the Conqueror came ashore at Pevensey from Normandy and within weeks defeated the English at the Battle of Hastings in 1066.

His large and well equipped fleet found no resistance as it arrived, a lesson not lost on future generations in Sussex.

They built fortifications at various times all along the coast at its most vulnerable places to prevent the enemy usually the French, from coming ashore again.

French forces did attack Sussex subsequently but never so systematically. Usually they confined themselves to raiding specific towns.

The most notorious examples were in the 16th century at Brighton. Details are a little hazy but the town was ransacked at least once.

There is some doubt as to whether there were raids in both 1514 and 1545 but the former date seems more likely. Brighton, then little more than a fishing village, was almost completely destroyed.

There were defences built later at Brighton and most other towns on the coast as threats from the French came and went.

But defences were built in a more organised fashion after the French Revolution and the rise of Napoleon in the late 18th century.

More than a hundred small forts, usually called Martello towers were built between Seaford in Sussex and Aldeburgh in Suffolk.

They formed a chain along the coast near the Continent although they never had to be put to use because Napoleon stopped short of invading Britain.

Just under half the towers remain and many have found other uses. The Seaford tower houses a popular local museum.

Even more substantial buildings were erected in the mid-19th century by order of Lord Palmerston when he was Prime Minister. A good example is the fort at Newhaven.

It took six million bricks to build it in a commanding position overlooking the harbour mouth. But the invasion never happened and the fort also survived two world wars without seeing any action. It is now a visitor attraction.

The remains of forts built at much the same time to protect Shoreham and Littlehampton at the mouths of the Adur and the Arun can still be seen. Again they were not needed against the French.

Last century the threat changed to Germany and in the Second World War the Government thought an invasion likely. Beaches were mined and closed to the public, central spans were taken out of Brighton’s Palace and West piers to prevent what might have been a rather incongruous entrance by the enemy.

The threat was real as was proved in 1944 when the allies started to win the Second World War by invading France at Normandy. But the Sussex defences once more didn’t have to be used.

By then, air power was a factor in wartime and airports such as those at Shoreham and Tangmere became as vital in defending the country as sea ports.

But that’s another story. Sussex can boast that as long as sea ports were the only means of defence, there was never another major invasion after 1066.