Aurelian: Birth of a Warrior: Book One.

Aurelian Pen Dreic is the second son of Legatus Uthyr Pen Dreic, of Guent, and is not expected to attain much in life. The last of the Roman legions had left Britain and the emperor had told the civil authorities to look to their own as the Saxons began to raid the east coast looking for captives, treasure and most of all, land.
Aurelian's adventures begin one day shortly before his sixteenth birthday while out with his childhood sweetheart, Lady Gwenna ap Teithfallt of Glywysing. The lad boy was taken prisoner while defending Gwenna and giving her time to escape.
Later that night while in camp Aurelian made good his escape and returned to Caerllion, to a hero's welcome and for his reward the king gave him a commission in his army, something the youngster had always dreamed about. From the age of eight he had shadowed the soldiers while they trained and today, he was given an honorary role serving with them.
His first task was to locate an old drunk in the town who had been telling tall tales about sunken ships and buried treasure, stories the old beggar had been telling for as long as Aurelian could remember. An expedition was put together which Aurelian would lead over the river Sabrinā and into a disused Roman Port, called Portus Abonae.
On arriving at the port Aurelian could see that this wild goose chase had been for nothing, only four buildings remained and they were badly burnt with the roofs falling in. If it was not for the sudden appearance of a Saxon Warband, Aurelian might have turned around and left the place as he found it. These Saxons knew the same legend. They were obviously working for someone with money enough to hire them and powerful so that they could walk unmolested by the High King's soldiers.