Designed as the "RMH" just before the 1952 merger of Riley-parent, the Nuffield Organization, with Austin to form BMC, the Pathfinder is seen as the last proper Riley car.

It used Riley's 110 bhp (82 kW), 2.5-litre — 2,443 cc (149.1 cu in) — twin-cam, "Big Four" straight-4 engine fitted with twin SU carburettors and had a separate all-steel chassis with coil spring rear (this was changed to leaf springs towards the end of production) and front torsion bar independent suspension.

The 12 in (305 mm) Girling drum brakes had a Clayton Dewandre Vac Hydro Servo fitted as standard.

The Riley was launched in 1953 and the Wolseley in 1954, and both were designed by Morris' Gerald Palmer for the Nuffield Organization before the merger.

An essential part of the location of the rear axle was a Panhard rod which on some early examples sheared on hard cornering resulting in the unfortunate 'Ditchfinder' nickname.