TAPLOW (near Maindenhead), ER 26th October 1989

At about 02:20 in the morning,  the 00:30 Whatley Quarry to Ripple Lane stone train (6L66) comprising of twenty-five 102-tonne bogie hopper wagons with a total weight of 2669 tonnes and being hauled by 56036 became derailed . A single DMU power car (55023) forming the 01:30 Paddington to Reading staff passenger train then struck one of the bogies (which had become detached from a derailed wagon) and was itself derailed. Nine people travelling on the passenger train suffered minor injuries. The DMU then fell onto its left hand side in the ten-foot between the Down Relief and the Up Main lines alongside the last two wagons of the freight train. Examination of the freight train showed that the accident was due to a failed monobloc wheel on the trailing axle of the first wagon to be derailed. A section of wheeltread was subsequently found six miles to the rear of the derailment. A similar accident took place on 3rd July 1990 between Immingham and Scunthorpe, again with cracks emanating from hot-stamp markings on the web of a wheel. Stringent inspection procedures were tightened  to identify suspect wheelsets following the accident.
HSE ; 4pp; f/o derailment plan (D.A. Sawer).

Information from Peter Mullen

Pictures at www.37025.com/Maidenhead_derailment.htm