The Class 390 is one of the fastest domestic electric multiple units operating in Britain, with a top speed of 140 mph; however limitations to track signalling systems restrict the units to a maximum speed of 125 mph (200 km/h) in service. In September 2006, the Pendolino set a new speed record, completing the length of the West Coast Main Line from Glasgow to London in 3 hours, 55 minutes, beating the 4 hours 14 minute record for the southbound run previously set in 1981 by its ancestor, British Rail's Advanced Passenger Train. The APT retains the ultimate speed record for this route, having completed the northbound journey between London and Glasgow in 3 hours 52 minutes in 1984.