Having undertaken a programme of station refurbishment, improved its ticketing arrangements and introduced new on-track plant and shunting locomotives, in 1969 the still embryonic Northern Ireland Railways set out to improve the Dublin-Belfast ‘Enterprise’ service, by replacing the existing diesel railcar sets with a locomotive hauled service. Intended to reduce the time for the 180 km journey to just two hours, the NIR Class 101 (DL) locomotives were designed to run in a push/pull configuration, with a 270 ton 8-car set of BR Mk.2b stock, at a maximum speed of 80mph.