sentences:  These successful locomotives worked, in the main, out of Waterloo and prior to electrification had a virtual monopoly of the Portsmouth expresses.Until the advent of the Bulleid Light Pacifics, a D15 was usually to be found working the Brighton to Plymouth service.Number 468 differed from the rest of the class in that it had the safety valves mounted on the firebox, with Urie N15 style dome and safety valve casings, whilst the others had Drummond direct-loaded safety valves on their domes.