The Boulton & Paul P.10 was a two-seat, single-engined biplane built just after World War I to develop techniques for the construction of all steel aircraft.

[1] In the first decade of the 20th century, Boulton and Paul besides their wood construction shops also had plants for iron making, wire fencing and structural steel for buildings.

Rather like the earlier P.6, the interwing gap was large and equal to the chord, putting the upper wing high above the fuselage.

The front fuselage was built on four tubular longerons, but from leading edge rearwards it consisted of a set of oval formers with stringers.

[5] This construction gave the fuselage a smooth, rounded "torpedo-like"[1] look, which was enhanced by the close cowling of the 100 hp (75 kW) Cosmos Lucifer radial engine, though its three cylinders projected out a long way for cooling.

[1] The P.10 was not the first metal British aircraft, for the unlikely looking Seddon Mayfly holds that priority; but it never had a realistic hope of flight.

[1] One lesser novelty, which was to become a standard Boulton & Paul feature was the mounting of the Lucifer on a hinge so that it could be swung sideways for servicing without disconnecting pipework etc.