The Inner Suburban Lines to and were electrified in 1976 with EMUs. In 1978 the electrification was complete to with EMUs providing the service. The route was then promoted as the Great Northern Electrics. The route between Hertford and Langley Junction, south of Stevenage, was also electrified but not regularly used by electric trains until 1979 when one Moorgate-Hertford service per hour was extended to Letchworth; prior to this diesel multiple units provided an infrequent service over this route, running between Hertford and Huntingdon/Peterborough. From 1979 until 1987 DMUs provided the service between Hitchin and Huntingdon/Peterborough. DMUs also provided a shuttle service between Royston and Cambridge between 1978 and 1988, connecting with the electric trains and replacing the former through Cambridge buffet expresses between Kings Cross and the university city.