service. Ash from the heavy fuel oil damaged the turbine blades, and the combustion chamber liner required frequent replacement due to damage. The electrical control systems were extremely complex for the time and gave much trouble; maintenance of the electrical equipment in a steam locomotive environment and knowledge base was difficult. Part way through its life one of the traction motors failed and instead of repairing or replacing it, it was simply removed, leaving the locomotive with only three traction motors and preventing it from achieving its full power output. It also suffered from the destruction of its heat exchanger in a fire at Temple Meads when combustion deposits in the exhaust side of the heat exchanger ignited. Fuel costs It was also much more expensive to run than expected. The efficiency of a gas turbine reduces dramatically at low power outputs so, to achieve respectable fuel economy, a gas turbine locomotive needs to be operated as much as possible at full power, with periods of part-load running reduced to a minimum. However, it turned out that, even on demanding express passenger schedules, it was not possible to operate the locomotive on full power for very much of the run and extended periods of part-load operation were inevitable, which resulted in heavy fuel consumption. It was also sometimes operated on the much more expensive and scarce light oil normally used only for starting, due to the level of wear caused by the ash from heavy fuel oil. Performance When reliable operation could be achieved, it did show itself capable of meeting expectations. Unfortunately, however, it was neither possible to achieve a consistently acceptable level of reliability nor to operate it under conditions which would allow reasonable fuel economy. Comparison of 18000 and 18100 The following table gives a comparison between 18000 and 18100. There are some anomalies and these are described in the notes. Post-BR use At the end of 1960, 18000 was withdrawn from operation and was stored at Swindon Works for four years. It then returned to mainland Europe, where for more than ten years it was used, in substantially altered (and no longer gas-turbine-powered) form, for experiments concerning the interaction between steel wheels and steel rails, under the auspices of the International Union of Railways. In 1975 it was moved to Vienna and displayed outside the Mechanical Engineering Testing building of the Arsenal research centre. Preservation In