History of the Metropolitan Police Service been headed by a Commissioner, rather than a Chief Constable which is the highest rank in police forces outside London. The first Commissioners to hold the post were Lieutenant-Colonel Sir Charles Rowan and Sir Richard Mayne. When Sir Charles Rowan died, leaving Sir Richard Mayne as the surviving Commissioner, Captain William Hay was drafted in to jointly run the force with Mayne. However, because the two Commissioners did not agree on methods of running the force, since 1855 it was decided that only one Commissioner would run the force. Metropolitan Police patrols took to the streets on 29 September 1829,
History of the Metropolitan Police Service 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. When Great Britain entered World War II 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 during 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