Britannia

Created by Jez Butterworth, Tom Butterworth and James Richardson, Britannia is a British historical fantasy series set during the Roman invasion of Britain in 43 AD. Kelly Reilly, David Morrissey, Mackenzie Crook and Zoë Wanamaker star in a story of Roman conquest, Celtic tribes, druids, prophecy and violent power struggles. The series blends ancient history with fantasy, mysticism and dark adventure rather than presenting the period as straightforward historical drama.

Från IMDB:
In 43 AD, the Roman Army returns to crush the Celtic heart of Britannia.