The Hart Engine Co. was based in Leeds. The engineer of the company, Mr. Redrup (see Redrup), built a 10-cylinder, 50 hp rotary engine, around 1910. (possibly with two rows of 5 cylinders),

-Later they built a 7-cylinder that gave 150 hp. A 9-cylinder 156 hp radial was built at Vickers Ltd.

-It is mentioned that there was another 9-cylinder rotary of similar power, 150 hp.

From Appendix 7: A 150 hp Hart engine was mounted on a Vickers FB.12, replacing another one of another brand that failed. This aircraft model installed several different engines.

“Vickers with Hart radial engine” (PiP-fmr)