The Excalibur Chronicles: Camelot Rising
The particulars might vary but the cycle remains the same; Mordred rises to try and gain control, an Arthur confronts him and balance is restored. But after fifteen hundred years of getting his butt kicked by various incarnations of his nemesis, Mordred decides to play dirty and kidnaps the prince that guards the gate to the Otherworld, unleashing havoc on modern day London.
When Adam Blythe pulls a sword from the ground and becomes the new cycle's Arthur figure, he finds himself and his best friend Clara thrown into a world of monsters, magic and murder. With the future unclear and the fate of the world in his hands, Adam must assemble his knights - individuals with supernatural gifts - and find Excalibur, the fabled weapon that will give him great power. However it won't be easy, when there are those around him who cannot be trusted and he has no way of knowing where Excalibur could be.