Seems to be an early version of MAD MAX Rail Truck...
A soldier of the King’s Own Royal Regiment on train escort in a truck adapted to run on rails. Other patrols used enclosed wagons. Train escort was,‘….a soul searing job which entailed sitting for hours in oven-hot iron trucks, lumbering slowly through deep defiles, bored, sweating and dirty.’ Lion and Rose Regimental Magazine, 1939. By kind permission of the King’s Own Royal Regiment Museum, Lancaster. (You could probably shorten this to basic 'A Britishsoldier on train escort duty during the 1936-39 Arab Uprising in Palestine. Copyright the King’s Own Royal Regiment Museum, Lancaster.'
Britain In Palestine, Brunei Gallery, SOAS, University of London