Marcos was founded in Dolgellau, North Wales, in 1959, by Speedex cars' Jem Marsh with aerodynamicist Frank Costin. Costin had earlier worked on the de Havilland Mosquito fighter-bombers and from there he got the idea to use plywood for the chassis.
In 1997 the Mantis name was re-used on a 2-seater coupé or convertible road car based on the LM series powered by the 4.6-litre all-aluminium quad-cam Ford 'Modular' engine producing 327 bhp (244 kW; 332 PS) and capable of 170 mph (270 km/h). To accommodate the engine the bonnet of the Mantis was significantly remodelled from the previous LM range (that used the Rover V8), and the upper chassis rails in the engine bay were widened. Price for the Mantis was £46,883.
In 1998 it was decided to supercharge the engine to produce one of the few British production sports car with over 500 bhp (373 kW; 507 PS), this being named the Mantis GT. It was first sold in Italy by Martes Spider Cars. Using a Vortech supercharger and intercooler the Mantis GT engine produced 506 bhp (377 kW; 513 PS), which could accelerate the car from 0–60 mph in 3.7 seconds. Price for the Mantis GT was £64,331.
Production of the Mantis was 51 cars, with 16 being the supercharged GT version (this does not include the Mantis Challenge race cars).