A Roman fortress near the city of Velsen served as the starting point for the Roman Emperor Claudius' campaign to conquer the island.

In late 2001, archaeologists discovered the ruins of an ancient fortress and items from the arsenal of Roman legionaries. The size of the excavated structure, as suggested by the Netherlands Research Council, indicates that it was a "castra" - a complex of buildings capable of accommodating thousands of soldiers.

Carbon dating of the wood used in the construction revealed that it dates back to the winter of 42 AD, a few months before the launch of the invasion into Britain. Roman soldiers crossed the English Channel, and soon most of the island became a province of the Roman Empire.

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The Roman presence near Velsen has been known since 1945 when pottery shards were found in the area.

The first fortress (Velsen 1), built in 15 AD and rediscovered in 1972, was the site of a fierce battle: archaeologists found slingshot pellets and human remains. Velsen 1 could house up to 1,000 troops.

Some researchers have suggested that Velsen 1, located 35 km from Amsterdam, is actually the ancient Flevum, a "castellum" or castle, which was almost completely destroyed by the Frisians in 28 AD, according to accounts of ancient historian Tacitus.

The second fortress (Velsen 2) was built near the first one under the orders of Emperor Caligula, the son of General Germanicus, who - lacking military accomplishments - sought to cover himself in military glory by conquering the island. Previously, Julius Caesar had occupied a small part of Britain for a brief period without incorporating it into the empire.

Both fortresses were built on the banks of the Oer-IJ river, a tributary of the Rhine, albeit on different sides.

Archeologists during their work at Velsen. Credit: Guardian

The fortress was erected both as a launching point for the Roman army to invade Britain and as defenses for the northern flank of the fleet from Germanic tribes. The garrison consisted of between 5,000 and 6,000 soldiers.

Archaeologists believe that Emperor Caligula personally visited the region to inspect the level of readiness for the planned invasion. This theory is supported by the discovery of several wine barrels with the initials of the sovereign, burned into the wood and found near Utrecht and Valkenburg.

Caligula did not see his dream fulfilled. He was assassinated by the Praetorian Guard before the invasion began in 43 AD, and all the praises for victory were claimed by his successor, Claudius. The Germanic tribes did not attack the new fortress. It was recognized as a structure of Roman origin after 1960 only.