automatic vacuum brake as described represented a considerable technical advance in train braking. In practice steam locomotives had two ejectors, a small ejector for running purposes (to maintain the partial vacuum at the correct level against inevitable slight air leaks in the train pipe and its connections) and a large ejector to release brake applications. The small ejector used much less steam than the large ejector but could not generate vacuum in the train pipe sufficiently quickly for operational purposes, especially in a long train. Later Great Western Railway practice was to use a vacuum pump instead of the small ejector – the pump was fitted to one of the engine crossheads and so did not use any steam, with the disadvantage that it only operated when the locomotive was in motion. The GWR favoured this due to the use of braking systems working on a vacuum level higher than other railways (see below) which would have required a relatively large and steam-hungry "small" ejector. Most steam locomotives of the period used straightforward live steam brakes on their own wheels (where steam pressure was let into the brake cylinders to apply the brakes), with the vacuum brake being solely used on the train. In such a case the two systems were usually operated proportionately by a single control, whereby the reduction in vacuum in the train brake system would open the valve feeding steam to the engine brake. It was unusual for any form of dedicated control to be provided solely for the steam brake – even when running with no train the driver controlled the engine's steam brakes by adjusting the vacuum brake system using the ejectors on the engine and the "head end" of the train pipe. This allowed the driver of the lead engine direct control over the brakes on any trailing locomotive (as well as the train itself) when double heading. With the introduction of diesel and electric locomotives by British Railways from the early 1950s, this same basic arrangement was carried over. BR's Modernisation Plan of 1955 called for, amongst other things, a long-term aim to switch to air brakes for both passenger and freight stock. The standard Mark 1 coaching stock had been designed and procured before the decision to switch to modern traction and air brakes had been taken, so the majority of the stock was fitted with traditional vacuum brakes. Air-braked goods