British Rail Class 29
The British Rail Class 29 consisted of 20 diesel locomotives which were rebuilt from the North British Class 21. The original licence-built MAN engines of the Class 21s had proved unreliable, so in 1963 locomotive D6123 was sent to Paxman's Colchester works to receive a new Paxman Ventura V12 engine.  A further 19 were re-engined in 1964–1965 at Polmadie Works, with other changes made at the same time. This included the fitting of four-character headcode displays in the nose ends. After rebuilding, they returned to service from Eastfield depot in Glasgow.