Complex sentence: The Pobjoy P was a British seven-cylinder, air-cooled, aircraft engine designed and built by Douglas Rudolf Pobjoy/Pobjoy Airmotors, becoming the progenitor of the R/Niagara/Cataract family of small radial engines.
Split into simpler sentences: The Pobjoy P was a British seven-cylinder, air-cooled, aircraft engine designed by Douglas Rudolf Pobjoy and built by Pobjoy Airmotors. It became the progenitor of the Pobjoy R/Niagara/Cataract family of small radial engines.