If war is a psychological game as much as a military one, this week in Afghanistan we suffered one of our biggest set-backs. The numbers add up to a painful equation. Six men dead. The single largest loss of British life in a single incident in Afghanistan since 2006. The roll-call of British men lost to this war tipping over 400. The sums left a nation in shock and thrust the issue of Britain's involvement in Afghanistan back onto the front pages.