In 55 B.C. Julius Caesar, commander of the Roman armies in Gaul, thought that it would improve his political image to invade Britain. The Celts in Gaul had been aided in their struggle against the Romans by the Celts in south eastern Britain and removing this source of help would be a benefit to the Romans in their operations to secure Gaul.
On August 26, 55 BC, Caesar set off from Portus Itius (Boulogne) with two Roman Legions (totalling about 10,000 soldiers). The next morning the Roman ships approached the cliffs of Dover, which were lined with British warriors ready to fight. Caesar decided to avoid these Celts, sailed several miles further northeast and landed on the flat, pebbled shore around Deal.
There were some minor skirmishes at the beach and four days later ships carrying a group of Roman cavalry were forced to return to France by a storm. The same storm seriously damaged the ships at Deal making the Roman legionnaires focus on repairing them.
During this time the Romans conducted some reconnaissance further inland and reported an abundance of grain crops and a large population.
Having no cavalry impaired Caesar's ability to conduct any large scale actions and after the ships were repaired Caesar ordered the Romans to return to Gaul.
The next year Caesar organised a second, much larger expedition consisting of five legions and 2000 auxiliary cavalry transported using a fleet of around 800 ships. Sailing from Boulogne they once again landed near Deal on the morning of July 6th.
The Celts withdrew in the face of such a large army and were pursued by the Romans to the Stour river, 12 miles inland. On the 8th July the Romans easily routed a force of Celts at a ford across the Stour near modern Canterbury. The Celts retreated once again, this time to a hill fort at Bigbury. The Romans were initially repulsed but after filling in the outer ditch and constructing a ramp they succeeded in capturing the fort.
Once again there was bad news for the Romans; the previous night a storm had wrecked most of the ships. The Legions were required to return and spend ten days building a defensive fort around the landing beach so that the ships could be repaired in relative security.
During this time the Celts re-organised and appointed a single leader, Cassivellaunus, chief of the Catuvellauni tribe.. The Romans won another battle at the Stour river and then chased the Celts north over the Thames.
At this point some of the Celtic tribes changed sides and informed Caesar that Cassivellaunus was located at a hill fort near Wheathampstead. With the Romans fast approaching his base Cassivellaunus ordered his loyal Celts to attack the Roman fort at Deal. The attack failed and Cassivellaunus surrendered to Caesar.
Caesar had been informed of mounting problems back in Gaul and wanted to return as soon as possible so his terms were lenient; the Celts were to pay an annual tribute to Rome - which, not surprisingly, never actually got paid!
The Romans left Britain in September and were not to return for another 97 years.