Sean Smith in Helmand province, Afghanistan

A British army sergeant, part of an Operational Mentor and Liaison Team, checks compounds during a patrol in Nawa district, Helmand province, Afghanistan Photograph: Sean Smith/Guardian

Afghan national army soldiers rest with troops during an early-morning OMLT patrol in Nawa district, Helmand. Under OMLT, US marines and British soldiers train and mentor the Afghan national army Photograph: Sean Smith/Guardian

Soldiers from the OMLT, working with the US marines to train the Afghan national army, cross a river on an early-morning patrol as they make their way to forward operating base Jakers in the Nawa district of Helmand Photograph: Sean Smith/Guardian

A British soldier, left, part of an OMLT, accompanies Afghan national army soldiers on patrol in Nawa district Photograph: Sean Smith/Guardian

British and American OMLT troops pass farmers carrying crops in Nawa district, Helmand as they accompany Afghan national army troops on a patrol Photograph: Sean Smith/Guardian

A British soldier with the OMLT in the Nawa district Photograph: Sean Smith/Guardian

American troops from the Second Marine Expeditionary Brigade exercise in a mortar pit at FOB Apache, which is under construction in the Nawa district of Helmand Photograph: Sean Smith/Guardian

A British soldier at FOB Jakers Photograph: Sean Smith/Guardian

A British soldier sits on a vehicle at FOB Jakers Photograph: Sean Smith/Guardian

British troops cool off in a canal after moving south from FOB Jakers to start a temporary patrol base in a clinic Photograph: Sean Smith/Guardian

British troops are watched by locals as they cool off in a canal Photograph: Sean Smith/Guardian