John Sadler was born and bred in Northumberland and he has worked for most of his career in the law. He is an expert on the history of warfare and a prolific writer on the subject. His many books include Battle for Northumbria, Scottish Battles, War in the North 1461-1464, Border Fury: The Three Hundred Years War, Culloden 1746, Bannockburn: Battle for Liberty and The Second Barons' War: Simon de Montfort and the Battles of Lewes and Evesham.