 The HST was introduced from 1976 on the Great Western Main Line between London Paddington and Bristol Temple Meads/Swansea, at a time when the maximum speed of British trains was 100 mph (160 km/h).A radical update of the standard BR livery was complemented by the 'InterCity 125' branding which also appeared on timetables and promotional literature.By May 1977 the full complement was in service on the GWML and they completely replaced locomotive hauled trains on the Bristol/South Wales routes.