Pre-Owned TT3021M BR Class 43 HST Train PackPre Owned Item, in as new condition. Test Run. Officially the fastest diesel trains in the world, the InterCity 125 High Speed Trains were introduced by British Rail in 1976, operating 125mph services on the Great Western Main Line and the East Coast Main Line before being introduced to other lines as their use spread. When originally built by BREL at Crewe Works the InterCity 125 units, consisting of a pair of Class 43 power units and a rake of Mk3