The greatest threat to London today is terrorism, but it’s easy to forget that this city was once one of the most heavily defended places on Earth. By the First World War, the entire southeast of England was layered with fortifications built to stop an invasion from across the Channel. The French tried. The Spanish tried.
The French tried again. The Germans tried. But in over two thousand years, London’s defenses were overwhelmed only twice: by the Romans in AD43, and by the Normans in 1066. Our story begins and ends on the coast, at Dover Castle, the most remarkable defensive site in England.
It was in continuous use from the Iron Age until the end of the Cold War — more than 1,500 years of defensive history tucked into one hillside. Today, it’s hard to see, but Dover Castle was built on the site of an Iron Age hill fort. Hill forts dotted the south of England back then, reflecting how violent and uncertain Celtic society really was. Take Beacon Hill in Hampshire, near Bclair.
The camp would have held huts, and faint outlines of them still remain. On top of the ramparts stood wooden fences and strong gates. And in bad times, people drove their livestock inside those walls for safety. In AD43, there was real danger: the invading Roman army.
Their first priority after landing was to establish supply bases, and the first and most important of those was at Richborough in Kent. You can still see its later masonry walls and the foundations of a great triumphal arch in the shape of a cross there today. The Romans founded London around AD50, anda at first, it was defended by nothing more than a ditch. That was a big mistake.
In AD61, Buudaca, queen of the Eini, led a revolt that completely destroyed the city. There were no survivors. Londinium took a while to recover, but when it rose from the ashes, it was a fortified town surrounded by a stone wall at least twenty feet high. You can still see part of it by Tower Hill Tube Station — the bottom half is Roman.
Above those original walls, medieval builders later added their own towers, as you can see by the Barbican Center today. London was the largest Roman town in Britain, but it wasn’t the only fortified one. Canterbury, originally settled by the Romans, sat on Watling Street, the road that led from Richborough to London. It too was ringed with tall walls, some of which survive to this day, although much rebuilt in the Middle Ages.
The Romans also left behind defensive forts. Pevenzy in Sussex, built in the 3rd century to hold back the invading Saxons, had walls that stood twenty feet high. But eventually, the Saxons overwhelmed it and slaughtered the defenders. Later, a Norman castle would rise inside those very walls.
The Saxon kings, in their turn, faced the next invaders: the Vikings. At first, they managed to push them back. But after a famous defeat on the watery causeway at the Battle of Molden in Essex in 991, the Vikings gained the upper hand and the Saxon grip on England began to slip. Yet the Viking victory was short-lived, because every school child knows what came next: in 1066, the Normans landed at Peveny Bay in East Sussex.
And unlike previous waves of settlers and invaders, the Norman conquest meant the ruthless imposition of an alien ruling class on the native population. The Normans achieved this largely through massive stone buildings. And the most important of those were the castles. These masonry structures were unlike anything England had ever seen.
By 1100, there were eighty-four of them across the country. The first was started at Pevenzy in September 1066. On his way to London, William the Conqueror received the surrender of the English leaders at Burkhamstead in Harfordshire, where another castle was raised. But his true goal was London.
He arrived in December, and there he built the greatest of all Norman castles, within the corner of the old Roman city walls. The White Tower — so called because it was once whitewashed — is the heart of the castle, though it was modified and added to right up until the building of a barracks in Queen Victoria’s reign. The Tower was begun, but never completed, by William the Conqueror himself. And we have to remember what it was really for.
It was built not to defend London, but to subjugate it and terrify it into submission. Royal castles went up strategically around London and all across England. But for the most impressive military one, we return to Dover, which was regarded as a crucial strategic location well into the twentieth century. Its great Norman tower still dominates the fortress despite a thousand years of modification.
Windsor’s Round Tower, although refaced and heightened in the nineteenth century, is still essentially Norman. Windsor has been occupied by the monarchy since the Norman period, making it one of the oldest continuously inhabited castles in the world. In Essex, there’s the less well-known but spectacularly sited Hadley Castle, originally built for Hubert de Burr in 1232 and later rebuilt by Edward III to guard the approach to the Essex marshes and the Tempame’s estuary. Little survives today because Edward VI, Henry VIII’s son, sold it off in 1551 and allowed its stone to be carted away for other building projects.
But it wasn’t only Norman kings who built castles. The great barons and the Norman bishops also asserted their authority with their own fortresses. The Archbishop of Canterbury built the tallest Norman keep in England at Rochester in 1127, guarding the river crossing that led to the south coast. The lesser nobility got busy too, establishing more modest fortresses.
In Aimsford in Kent, an early Norman castle built around a small hall inside an oval enclosure is typical of the smaller castles of the conquest. It was built by William de Ainsford, who ruled the surrounding land in the king’s name and held the power of life or death over the locals. And Pleshim in Essex shows the impact of the Norman invasion better than almost anywhere else. It has a fifty-foot high mound, called a m or, upon which the keep was built, anda lower bailey with ramparts rising thirty-six feet above the moat.
It was built by Jeffrey Demandville in the center of his new lands, and around it grew a fortified township that is almost the same size today as it was in Norman times. By the end of the fourteenth century, castles had to change. Bodum in East Sussex combined up-to-the-moment defensive features like gunports and powerful circular towers on each corner, but it also offered sumptuous accommodation around a central courtyard. They say that in the late fourteenth century, it boasted thirty-three fireplaces and, amazingly, twenty-four lavatories built into the walls, complete with drainage that flushed straight into the moat.
Not far away stands another perfectly symmetrical moated castle, this one built of brick. Hzman Zoo in Sussex, like Bodum, couldn’t really have resisted artillery fire. It was more of an elegant, sophisticated residence than a proper fortress. And the truth is, from Henry VII’s reign onward, all real fortifications belonged to the state.
. Equally important was the rise of the Royal Navy. That meant the first line of defense was now the fleet, and defenses in and around London played a supporting role to sea power. Some forts were still built to repel specific threats.
Between 1539 and 1542, Henry VIII built a spectacular line of coastal defenses stretching from Hull in Yorkshire to Milford Haven in Wales, intended to protect England from seaborne attack by the Catholic powers of Europe. Deal Castle, one of the finest of these, was built to guard the Kent coast and the naval anchorage of the South Downs. Its revolutionary shape was designed to maximize the effect of artillery, and the design came straight from Italian military engineering. Other forts, like Tilbury on the Tempame estuary,protected the river approach to London.
Started by Henry VIII but massively enlarged by Charles II’s brilliant military engineer Bernard de Gome, Tilbury added earth angle bastions to its pure masonry walls, designed to absorb the impact of cannonballs. Upner Castle was built by Queen Elizabeth to defend her new naval dockyards at Chattam. And it was actually put to the test in 1667, when the Dutch Navy sailed up the Medway. Its guns fired until their powder was exhausted, but the Dutch sailed through anyway, and the English fleet was burnt.
Charles II was humiliated. After that, the land defenses for the Chattam dockyards were strengthened in the eighteenth century, creating the string of forts now known as the Chattam Lines. They were never put to the test, but Fort Amhurst, with its brick and earth ramparts, survives today from that period. Some of the greatest fortresses built since the Middle Ages went up to repel Napoleon’s French army, between 1792 and 1814.
The period of greatest danger was after 1803, when a magnificent series of coastal fortifications was constructed under the supervision of Lieutenant Colonel William Twist. The most impressive, and certainly the largest, wasguess where? Back at Dover. The Western Heights, as it’s now known, was a massive holding depot from which up to six thousand troops could sally forth to repel the French army once it landed.
But that was only the largest set piece in a remarkable system. In 1803, the Martell tower system was developed to protect the more isolated sections of coastline. Those circular brick towers were designed to protect the marshy ground between the sea and the firm land, and they would have raked the landing French troops with musket fire. Many of those towers today have been converted into charming seaside homes.
Barracks construction got a boost here at Wulitch after the Crimean War, when Florence Nightingale and others proved that if a soldier’s living conditions improved, so did his morale. The greatest of the Georgian barracks was begun at Wulitchin 1774, built to house more than three thousand officers and men of the Royal Regiment of Artillery. By the time it was finished, it had become the longest building in Britain. In the mid-1850s, major technological developments made every existing fortification on the South Coast obsolete almost overnight.
The first was the development of new ironclad warships and troop carriers. But perhaps the bigger threat was the invention of the explosive shell. Instead of firing solid lumps of metal like cannonballs, artillery could now fire bombs that exploded on impact. Those new shells could reach a target nine thousand yards out to sea, compared to a measly two thousand yards with solid shot.
In response to this growing threat,and to Prime Minister Palmyon’s fear that Napoleon III of France was planning his own invasion, a new series of forts went up. Chattam was again a major focus. Circular forts were built in the river Medway as platforms for the new guns. Fort who, built on a marshy island, was what we call casemated — the casemates were the mountings for guns and their magazines.
This amazing line of defensive forts stretched right the way around the south coast to Milford Haven in Wales. The river Tames was also fortified, including Colehouse Fort and Cliff Fort,rushed up as an answer to the French threat. But the threat never materialized, and all those forts have since been known, unkindly, as Palmyon’s Follies. By the late Victorian period, everyone agreed it was impossible to protect London with a single ring of fortresses.
Instead, a series of so-called mobilization centers went up along the North Downs — permanent positions where artillery and troops could be stationed if invasion threatened. Thirteen centers were eventually built, including one at Holstead that is still a military base today. Their true successors came after the fall of France in 1940. To repel the anticipated Nazi invasion, over seventeen thousand pillboxes — so named because of their shape — were built between 1939 and 1941.
Tank traps went up all around London, and many still exist. You can see concrete ones next to Wavely Abbey in the heart of Surrey. But those were among the last structures ever built for land defense in this country, because by the twentieth century, the defense of London had shifted to the air. Air power became a factor in the First World War, when a new kind of military installation was invented: the airfield.
Hawking in Kent was one of the first Royal Flying Corps airfields, and it’s still the nearest airfield to France. A museum and a few abandoned buildings mark what remains of that historic site. After the war, engineers tried to detect aircraft engine noise coming across the Channel as an early warning system. An experimental listening station survives at Greatstone on the Kent Coast,built between1927 and1930.
All that remain are extraordinary curved shapes that once collected the sound. But it was radar that truly transformed England’s air defenses. The best surviving chain of Second World War radar stations is at Swinggate, east of Dover Castle. London’s anti-aircraft batteries played a crucial role in the Battle of Britain, and although most are now gone, one of the largest batteries ever built still exists at Iwway in Kent.
Its 5. 2-inch guns were a key part of London’s defense in 1940 and41. And finally, we come back to Dover. After the war, the castle was chosen as one of ten nuclear strongholds in case of war with Soviet Russia.
After the Cuban Missile Crisis in 1962, a World War II command center in tunnels in the cliff face was refurbished as part of the Cold War defense lines. Those tunnels stayed in use until 1984, when operations moved to an underground bunker near Crobra. Today, that site is in the hands of Sussex Police. To the Norman military engineers who built these castles, the idea that London could be defended by underground command centers linked to airfields would have been inconceivable.
Yet despite all the vast changes in how the capital was defended, there has been astonishing continuity. Tilbury Fort was as important to Henry VIII as it was to Winston Churchill. Even the Tower of London featured in Churchill’s plans for the end of the Second World War. Rudolph Hess was briefly imprisoned there, in the same tower where Sir Thomas Moore had been locked up four hundred years before.
But of them all, Dober Castle is the most remarkable — a place where visitors today can see every single stage of the defense of England. I suspect if there were enough room for a runway, it would still be in use today.
