acted upon by the inspectorate): Critics at the end of the 1850s also noted that during the Crimean War, the Grand Crimean Central Railway had been built to forward supplies from Balaclava to British siege lines not by the Royal Engineers, but by a consortium of civilian railway contractors. If the government turned to civilians as best fitted to build a military railway, was it not anomalous that it thought military engineers best fitted to inspect new railway lines? Extension and formalisation of powers The inspectorate's powers were extended and formalised by the Railway Regulation Act 1871 ('An Act to amend the Law respecting the Inspection and Regulation of Railways'). Paragraph 4 extended the power to inspect to give inspectors explicit powers to require the production of persons and papers by a company being inspected. Paragraph 5 meant new works on existing lines were liable to the same inspection regime as new lines. The BoT could now set up a formal court of inquiry to investigate an accident, taking evidence on oath in public hearings. Inspectors investigating an accident were now required to make a formal report to the BoT, which was now empowered to publish reports (from an inspector or from a court of inquiry) directly. Subsequent public inquiries under the new powers included those into the Shipton-on-Cherwell train crash in 1874 (chaired by an inspector William Yolland), and into the Tay Bridge disaster of 1879. However, the procedure fell into abeyance after the failure of the three-man board (of which Yolland, by now chief inspecting officer, was a member) of the Tay Bridge inquiry to arrive at an agreed report. For many years in the mid-19th century the Railway Inspectorate advocated in its accident returns and otherwise three safety measures it saw as vital to ensure passenger safety: "lock" Interlocking of points and signals, so that conflicting signal indications are prevented; "block" A space-interval or absolute block system of signalling, where one train is not allowed to enter a physical section until the preceding one had left it; and "brake" Continuous brakes, to put at the command of the engine driver adequate braking power; this requirement being increased as the technology made it reasonable to 'automatic' (in modern parlance 'fail-safe') continuous brakes which had to be 'held off' by vacuum or compressed air and would be applied automatically if that supply was lost (e.g. if a train were