Saint George for England by G. A. Henty (1832 - 1902)

A tale written for children in 1885.
It tells of a child of noble birth whose parents have fallen foul of the current royalty. He is placed in hiding and grows up with a bowyer and then apprenticed to an armourer just outside the gates of the City of London.
He becomes accomplished in arms and joins the campaign in France where we see the battles of Crecy and Poitiers through his eyes.
A tale of heroism and 14th century viciousness. Great fun. (summary by jimmowatt)