It's a Sizaire-Berwick modified by the Admiralty in 1915 for potential use by RNAS squadrons in Africa and the Near East, known as the "Wind Wagon".
Sizaire-Berwick was an Anglo-Scoto-French cooperation - the engineering by Maurice Sizaire, formerly of Sizaire-Naudin, the orders from F.W. Berwick in London and the cash from the Keiller marmalade family. The first cars were similar to a contemporary Rolls-Royce (to the point of having to modify the looks to avoid legal action).
