Too many answers, and none of them complete. Also, the information I have is incomplete or contradictory.
The car is a Rawlson CR6. For all the information on the internet to be correct (!), more than one of these needs to have existed. Gerry Marshall's son indicates "the" CR6 was rebodied to become "the" CR7.
My source indicated the engine was called Holbay, although it may simply have been an MAE prepared by Holbay, or equipped with a Holbay head.
A former owner of this car:
http://www.autopuzzles.com/forum/index.php?topic=29513indicates that Mike Rawlings bought the Lotus-Rotorvic, rebodied it and changed the engine, creating the Rawlson CR6. The Rawlson competed for several years. After retirement, it was eventually re-united with the Rotorvic V12.
One point awarded to nicanary for being close enough.