Simon Fowler is a professional researcher, writer and tutor specialising in history. In recent years he has researched dozens of men and women who served across the world during the two worlds wars and given many talks on the subject.
His Tracing Your WW1 Ancestors' book is the most comprehensive guide to the subject currently in print. Copies can be bought from the Pen & Sword Stand. Look out too for his guides to Army and Navy ancestors.