The British Rail Class 21 was a type of diesel electric 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 Thirty-eight of the locomotives were withdrawn by August 1968; the rest were rebuilt with bigger engines to become Class 29, although those locos only lasted until 1971.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