A Type 2 loco, built in the late-1950s by The English Electric Co. Ltd. at Vulcan Foundry, Newton-le-Willows.  They were fitted with one 9-cylinder Napier Deltic engine rated at 1100 bhp.
 
The were called 'Baby' Deltics because of the engine being smaller than the 18-cylinder engines fitted to their Type 5 brethren (later Class 55), not because they bore any resemblance to them.

In September 2010 The Baby Deltic Project announced its intention to create a replica of an EECo Type 2 (Class 23) ‘Baby’ Deltic, using its Class 37 test-bed loco as the starting point. 

In brief, the Project intends to shorten the nose and body length of the 'donor' loco, restyle the body and mount the loco on Class 20 bogies so as to reproduce, so far as reasonably practicable, the appearance of a Class 23.  It is not as simple as it seems, the apparantly simple act of shortening the nose ends involves more work than the shortening of the body section for example. To mount Class 20 bogies onto a Class 37 underframe requires the modification of the entire centre casting, pivot members and side-bearers as well as all the bracing and load concentration points.