Sussex /ˈsʌsɪks/, from the Old English 'Sūþsēaxe' ('South Saxons'), is a historic county in South East England. Evidence from a fossil of Boxgrove Man (Homo heidelbergensis) shows that Sussex has been inhabited for at least 500,000 years. It is thought to be the oldest human fossil ever discovered in Britain. Prior to Roman invasions it was occupied by a Belgic tribe called the Atrebates. Togibubnus ruled over much of Sussex when the Roman conquest of Britain began and formed most of the Roman canton of the Regni.