The Fields of Britannia : The Darkness Before the Dawn

It's the year 367 AD, and the Roman military presence in quiet Brittania has dwindled to a mere few thousand legionaries made up of green recruits and tired veterans, with the mightiest of the legions having been pulled out of the province to fight in the gigantic power struggles for the Imperial throne, as Emperors rise and fall with astonishing speed.
Not unnoticed by the barbarian tribes beyond Hadrian's wall and across the Irish sea, or by the fast-growing Saxon presence beyond the Rhine, the enemies of Rome begin to make plans to bring fire and blood to Britannia, and remove the Roman presence from the island for good...
In a story that will take you across England from the coast of Dover to the very edge of the Roman Empire, our heroes will be beset by enemies on all sides and have to fight against despair, overwhelming odds and their own prejudices in order to pull together and survive the onslaught.