An 8 inch Howitzer Mk 6 of the 1st Australian Siege Battery (formerly 54th Battery, 36th (Australian) Brigade Royal Garrison Artillery), in action at Voormezeele.
This gun, at the time, was not on a Vickers platform as shown by the large scotches behind the wheels. The photograph was taken at the moment of extreme recoil, after the gun had just fired and the blur of the landscape in front of the muzzle is due to the discharge of the heated gas.

Pictured, left to right: 684 Gunner (Gnr) E A M Ray; 118 Bombardier A J Marlin; 286 Gnr H Byars; next two unidentified; 325 Corporal R A O'Brien Croix de Guerre, Battery Sergeant Major (facing the camera); unidentified.

Note the sandbagged area in the foreground.