 From before Roman times, slavery was normal in Britain, with slaves being routinely exported.Slavery continued as an accepted part of society under the Roman Empire and after; Anglo-Saxons continued the slave system, sometimes in league with Norse traders often selling slaves to the Irish.In 870, Vikings besieged and captured the stronghold of Alt Clut (the capital of the Kingdom of Strathclyde) and in 871 took most of the site's inhabitants, most likely by Olaf the White and Ivar the Boneless, to the Dublin slave markets.