Here is Corporal William Harmer, who served with the 10th (Service) Battalion (Cornwall Pioneers), Duke of Cornwall's Light Infantry.
The 10th Battalion was raised at Truro in March 1915 by the Mayor and the City, and trained at Penzance before moving to Hayle in October. In June 1916 they landed at Le Havre, fighting on the Western Front until the end of the war.
We don't know a great deal about William but he came from the Penryn area. During the conflict he was awarded the Military Medal.
My book, 'Cornwall In The First World War', is published by Truran. With 112 pages and 100 images, you'll find it in bookshops across the Duchy. It's also available through Amazon: http://amzn.to/19JbtZm