The designation "CG" continued the tribute to Cesare Gariboldi, a Leyton House March team manager who died in a road accident in 1989. Five CG901 chassis were constructed during the season. Chassis 001 was later modified to accommodate the Ilmor 2175A engine the team would use in 1991, providing a development bridge to the following year's car.
The CG901 was built around an evolution of the CG891 but taken to greater aerodynamic extremes. Newey prioritised aerodynamic efficiency above almost all else, which produced a car highly sensitive to pitch and roll, requiring a very stiff suspension setup to maintain its intended aerodynamic platform.
The monocoque was a carbon fibre composite tub encapsulating the driver, front suspension dampers, and fuel cell. The cockpit was notably cramped; two external blisters were visible on the lower tub to accommodate the drivers' heels in the narrow footwell. Front suspension dampers sat ahead of the driver's feet, of the two-way adjustable Koni type, actuated via rockers and pushrods from the front uprights.
The nose section was detachable, incorporating a front wing bolted from the underside and sitting proud of the nose itself. The Judd EV engine was attached to the tub via studs and acted as a fully stressed structural member. The cooling layout drew on Newey's prior experience with Indycars, using two large water coolers fed through a water-oil heat exchanger in the right-hand sidepod. The gearbox was a six-speed longitudinal unit attached through a bell housing that formed the lower section of the engine oil tank, with the selector mechanism positioned at the front of the assembly — an unusual arrangement that differed from most contemporary layouts. Electronics were principally supplied by Zytek Engineering, with a Marelli ignition package used for at least part of the season.
The car appeared in two distinct specifications across the season. The early-season A-spec suffered aerodynamic problems traced to erroneous data from the team's wind tunnel. The B-spec update, introduced at the French Grand Prix, addressed these with a new aerodynamic floor building on established exhaust-fed diffuser practice, alongside a revised engine cover that was extremely narrow and tightly sculpted around the tub.
The A-specification CG901 was slow and uncompetitive in the first half of the 1990 season as the team struggled to understand the aerodynamic data discrepancy. The B-specification car transformed the picture. At the French Grand Prix at Paul Ricard both Capelli and Gugelmin showed dominant form, bewildering rivals with far greater budgets and resources. The pattern was repeated at the British Grand Prix at Silverstone, where the team again appeared capable of winning. Both performances raised hopes that the Leyton House CG901 could be a genuine race-winning threat.
For the remainder of the season, however, form reverted to being patchy and the car was plagued with reliability failures, preventing either driver from converting pace into podiums or points on a consistent basis.
The CG901 stands as one of Formula One's most compelling might-have-beens. Its two mid-season performances in 1990 demonstrated that a small, under-resourced team could produce a car capable of outrunning the sport's establishment when Adrian Newey's aerodynamic thinking was functioning as intended. The experience also foreshadowed the direction Newey would take at Williams, where he would go on to design a series of dominant championship-winning cars through the 1990s. The Leyton House turquoise livery and the memory of France and Silverstone 1990 have made the CG901 an enduring icon of the era.