That would appear to be a sun hat plus two wicker baskets jerry cans, and early british fuel tins, boxes, and possibly one piece of summerfield tracking resting against the left of the trailer. On the left side of the tank at the front there appears to be an insignia, and ajacent to possibly the front and centre compartments two white crosses in chalk. I would think the hose has been used as gravity drainage, or to connect to remote pumping, to either fill or discharge. There should be a record of the vehicles and equipment allocated to the unit. It seems that they were not short of tin mugs.