Evidence from a fossil of Boxgrove Man Homo heidelbergensis shows that Sussex has been inhabited for at least , years. It is thought to be the oldest human fossil ever discovered in Britain.
Near Pulborough, tools have been found that date from around 35, years ago and that are thought to be from either the last Neanderthals in northern Europe or pioneer populations of modern humans. The county is also rich in remains from the Bronze Age and Iron Age. Prior to Roman invasions it was occupied by a Belgic tribe called the Atrebates. Togidubnus ruled over much of Sussex when the Roman conquest of Britain began and formed most of the Roman canton of the Regni.
Under St Wilfrid , Sussex became the last of the seven traditional kingdoms of the heptarchy to undergo Christianisation. By the 8th century the kingdom had expanded to include the territory of the Haestingas.
Around in the aftermath of the battle of Ellandun , Sussex was annexed by the kingdom of Wessex , a kingdom that with further expansion became the kingdom of England. Defeating Harold at the Battle of Hastings , William the Conqueror established five later six semi-independent territories known as rapes within Sussex.
Castles were built, many the subject of sieges in the High Middle Ages. Sussex was of strategic importance on the most direct route between Angevin lands in England and Normandy. Many Sussex ports, including the Cinque Ports , provided ships for military use.
