To my 19-year-old son, World War I — which ended 100 years ago yesterday — is as remote an event as the Congress of Berlin was to me when I was his age. To my generation, World War I was not quite history. My father’s father, John Ferguson, had joined up at the age of 17 and fought on the Western Front as a private in the Seaforth Highlanders. He was one of more than 6 million men from Great Britain who served. Of that number, 722,785 did not come back alive. Just under half of all those who lost their lives were aged between 16 and 24 — a fact that never fails to startle.