<P> Along with law enforcement within the Metropolitan Police District, the Metropolitan Police also had responsibility for the policing of the Royal Dockyards and other royal naval bases between 1860 until 1934, including Portsmouth, Chatham, Devonport, Royal Naval Air Station Pembroke and the Royal Woolwich Arsenal . They also policed Rosyth Dockyard from 1914 until 1926 . </P> <P> Before the 1970s, police forces often called for assistance from the Metropolitan Police because of their detective experience . The last case of this was when the now defunct Buckinghamshire Constabulary called upon the MPS to help in the investigation of the Great Train Robbery . </P> <P> In 1931, Hugh Trenchard was appointed as Police Commissioner Trenchard served as head of the Metropolitan Police until 1935 and during his tenure he instigated several changes . These included limiting membership of the Police Federation, introducing limited terms of employment and the short - lived creation of separate career paths for the lower and higher ranks akin to the military system of officer and non-commissioned career streams . Perhaps Trenchard's most well known achievement during his time as Commissioner was the establishment of the Hendon Police College which originally was the institution from which Trenchard's junior station inspectors graduated before following a career in the higher ranks . </P> <P> When Great Britain went to the War on September 3, 1939, the strength of the Metropolitan Police stood at 18,428, which was 900 officers short of full strength . Due to the increased responsibilities of the police war time, three reserve groups were mobilised . The first consisted of 2,737 ex-police pensioners who were re-engaged, a second of 5,380 Special Constables serving on a full - time basis for the duration of the war, and the third being 18,868 War Reserve Constables employed on the same basis as the Special Constables . On the same day as the Battle of Dunkirk, Scotland Yard issued a memorandum detailing the police use of firearms in wartime . The memorandum detailed the planned training for all officers in the use of pistols and revolvers, as despite the police being a non-combatant force, while the war was in progress they would be responsible for providing armed protection at premises deemed at risk from enemy sabotage and would assist the British Armed Forces in the event of an invasion . Due to these added roles, on 1 June 1940, 3,500 Canadian Ross Rifles and 72,384 rounds of . 303 ammunition were received from the military and distributed among divisions . Thames Division were allocated the smallest amount of 61 rifles, and "S" Division the largest with 190 . Fifty rifles were also issued to the London Fire Brigade and the Port of London Authority Police . </P>

In 1805 which city employed the first black police officers in the u.s