unable to alert the inhabitants of a premises on fire. Following the Siege of Sidney Street in 1911, one thousand self-loading Webley & Scott pistols were purchased. In 1914, the Bulldogs were withdrawn from service and returned to stores. Lord Trenchard standardised the issue of pistols among divisions with the number of firearms issued depending on the size of the area; ten pistols with 320 rounds of ammunition were issued to divisional stations, six pistols with 192 rounds per sub-divisional station, and three pistols with 96 rounds to each section station. In 1936, the authorisation to carry revolvers on outer districts was revoked, and at the same time Canadian Ross rifles were purchased in the prelude to the Second World War. A review in 1952 following the Derek Bentley case found 15% of firearms in service to be defective; leading to Special Branch and Royalty Protection Officers being re-armed with an early version of the Beretta semi-automatic pistol. Armed response vehicles Armed response vehicles (ARVs) deployed for the first time in London during 1991. Following their success, forces outside of the capital later formed them throughout the early to mid-1990s. The concept of an ARV was influenced by West Yorkshire Police's Instant Response Cars, as used in 1976. Early ARVs contained a secure safe between the seats containing a .38 Smith & Wesson Model 10 for each member, with two 9 mm Heckler & Koch MP5 semi-automatic carbines secured in the boot. After ARVs became established, and the practice was accepted for widespread use, the Model 10 revolvers were replaced by more recent self-loading Glock 17s, firing 9 mm rounds. Revolvers and pistols could be removed from the secure safe by ARV members, if an "immediate threat to life" was posed, in the opinion of the ARV member. Authorisation to remove carbines required authorisation from the control room once they had contacted an officer of Association of Chief Police Officers (ACPO) rank. If a high-ranking officer could not be sought to gain authorisation, such could be given by a Chief Inspector in an emergency. In recent years ARV members have carried their personal pistols on them as a matter of routine, and equipping of carbines rests on the judgement of the individual officer, although the control room must be informed of events. Formation As it was originally named, the Firearms Wing (designation D6) was formed as part of the Civil