train accidentally dividing, or by careless coupling of the hoses, or otherwise) the vacuum brake on the entire train was useless. In response to this obvious defect, the automatic vacuum brake was subsequently developed. It was designed to apply fully if the train became divided or if a hose became displaced. The automatic vacuum brake was slightly more expensive to manufacture and install than the simple system due to it requiring a higher number of machined parts, and incurred higher running costs since the ejector ran continuously (at a cost in steam and thus fuel and water) to maintain the vacuum when the train was running, rather than only being used when braking as in the simple system. Opposition to the fitting of the automatic type of brake on the grounds of cost (particularly by the LNWR and its chairman Richard Moon - as one of the largest British companies, the refusal of the LNWR to adopt the automatic brake was a strong factor against its wider use by other companies, especially those interchanging traffic with the North Western) meant that it took a serious accident at Armagh in 1889 before legislation compelled the adoption of the automatic system. In this accident at Armagh, a portion of a train was detached from the locomotive on a steep gradient and ran away, killing 80 people. The train was fitted with the simple vacuum brake, which was useless on the disconnected portion of the train. It was clear that if the vehicles had been fitted with an automatic continuous brake, the accident would almost certainly not have happened, and the public concern at the scale of the accident prompted legislation mandating the use of a continuous automatic brake on all passenger trains. In continental Europe, the vacuum brake was sometimes called the Hardy brake, after John George Hardy of the Vacuum Brake Co, 7 Hohenstaufengasse, Vienna. Operation In its simplest form, the automatic vacuum brake consists of a continuous pipe—the train pipe—running throughout the length of the train. In normal running a partial vacuum is maintained in the train pipe, and the brakes are released. When air is admitted to the train pipe, the air at atmospheric pressure acts against pistons in cylinders in each vehicle. A vacuum is sustained on the other face of the pistons, so that a net force is applied. A mechanical linkage transmits this force to brake