British Vickers machine gun crew wearing PH-type anti-gas helmets. Near Ovillers during the Battle of the Somme, July 1916. The gunner is wearing a padded waistcoat, enabling him to carry the machine gun barrel. See Image:Vickers machine gun crew with gas masks rear view.jpg for an alternate view of this crew.
Source: Imperial War Museum catalogue number Q 3995.
Photo: Lt. J.W. Brooke