BHP was formed by the well-known engine man Frank Halford, in co-operation with Beardmore. The initials standing for Beardmore Halford Pullinger. The company existed mainly to build copies of the in-line Austro-Daimler aero engine, the source for so many aero designs across Europe in the 1920's. Up to thirty engines of other makes were originally copied from the Austro-Daimler.
The BHP Co was eventually merged into Siddeley as the design flaws in the original BHP engine proved to be beyond the facilities at BHP to sort out.
Halford, starting out on a long and distinguished career in the aero-engine industry, moved to Siddeley-Deasy (Siddeley) with the assets of BHP.