The 21 was a car made by Lanchester between 1923 and 1932. A total of 735 were made. The car was first shown at the 1923 Motor Show and sold alongside the Lanchester 40.

The 21 was fitted with a 2998cc six-cylinder engine (later models were fitted with a 3340cc six-cylinder engine). The engine had single overhead camshaft and was connected to a four-speed gearbox via a single-plate clutch. The engine produced 60bhp and the car had a top speed of 63mph (101kmh), the later models could reach 70mph (113kmh).

The chassis was available in two sizes, the 10ft 9in (short chassis) and the 11ft 1in (long chassis). The chassis was fitted with semi-elliptical leaf-springs in the front and cantilever suspension in the rear. Brakes were fitted on all four wheels which were rod-operated. In 1930 a Dewandre servo was fitted as standard to the car.

The tourer cost £1250 in 1923.

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