Early Republican Denarius found in Britain
It was either brought by a Roman soldier after the invasion - it is very worn, and coins could stay in circulation for centuries since their value lay in their metal content
It came to Britain in the late third century BC, as a result of trade. The Greeks had traded with Britain, originally via the Carthaginian colonies; Cornish tin was a key component of those Greek bronzes we so admire.
Silver coin dating to 211 BC is oldest piece of Roman money ever found in Britain - Daily Mail