Unidentified Villiers powered flat tanker

Does anyone recognise this motorcycle? I would guess it is from between 1914 and 1919, the Villiers engine is an easy enough spot but I can't elaborate any further. There's something on the petrol tank but I can't make it out. If you reckon you know what it is please comment.

Whatsit? Unidentified Villiers flat tanker.

Postscript: thanks to the comment from 'anonymous' that identified the machine as an Ixion.