The British Rail Class 21 was a type of diesel Hydraulic locomotive built by the North British Locomotive Company in Glasgow for British Railways in 1958-1960. They were numbered D6100-D6157. Thirty-eight of the locomotives were withdrawn by August 1968; the rest were rebuilt with bigger engines to become Class 29, although those locos only lasted until 1971.

The Dapol OO Gauge model of the Class 21/29 features:

Detailed body with etched grilles and separately fitted handrails

Finely detailed cast wheels

Metal sprung buffers

5 pole Super creep motor with twin brass fly wheels for controlled pulling power and incredible slow running speed

All wheel drive and pick up

Independent directional and cab lighting

DCC Ready with provision of an MTC 21 pin socket

Accessory bag with optional fitted components