April 2004: Sgt Mills and his platoon of snipers fly into southern Iraq, part of an infantry battalion sent to win hearts and minds. They were soon fighting for their lives. Back home we were told they were peacekeeping. But there was no peace to keep. Because within days of arriving in theatre, Mills and his men were caught up in the longest, most sustained firefight British troops had faced for over fifty years. For six months, they fought alone: isolated, besieged and under constant enemy fire.