It’s 2015, and Camelot and Sherwood are at war.

The Circle, the UK paramilitary agency whose Knights carry the devices of the members of King Arthur’s Round Table, is hunting the Green Chapel, eco-activists allied to Robin Hood’s Merry Men. For the Knights, this quest is personal as well as political: the Chapel’s leader, Jory Taylor, is himself an errant Knight – and he has stolen the Holy Grail from the British Museum.

But this war is fought with modern weapons, and nowhere – from the Circle’s Thameside fortress to a Bristol squat, from the oldest pub in England to a music festival in Cheshire – will remain untouched.

Before long, the enmity between its greatest heroes will tear Britain apart.