 The InterCity 125, otherwise known as the "High-Speed Train" (HST), was launched in 1976 with a service speed of and provided the first high-speed rail services in Britain.The HST was diesel-powered, and the Great Western Main Line (GWML) was the first to be modified for the new service.Because the GWML had been built mostly straight, often with four tracks and with a distance of 1 mile (ca.