After successfully racing their single-seater Marauder racing car the pair left Rover in 1950 and formed Wilks, Mackie and Company to exploit their idea of a two-seater sports car based on the new Rover 75 chassis.

Spencer King was later famous for his involvement in many Rover and Leyland Group designs.

In view of the much lighter 2/3-seater (a single bench seat but the seats were separated on the "100"[1]) open[note 1] coachwork the engine was moved back to improve handling and front / rear weight distribution.

[2] The 6-cylinder, inlet over exhaust valve, 2103 cc Rover engine was slightly modified with higher compression ratio to raise the output by 5 bhp (4 kW; 5 PS) to 80 bhp (60 kW; 81 PS) whilst the 100 version was bored out to 2392 cc and fitted with triple SU carburettors to give 105 bhp (78 kW; 106 PS).

The UK government doubled the already high level of Purchase Tax on cars with a pre-tax price above £1000.