The Metropolitan Police website has a bunch of info, including a fairly detailed timeline, about policing in London since the creation of the original Bow Street Runners in 1748. This is a summary of that timeline.

• 1748: Bow Street Runners started
• 1763: Introduction of the Bow Street Horse Patrol
• 1789: Marine Police Founded
• 1829: September, formation of Metropolitan Police
• 1830: First MET officer to be killed on duty, PC Joseph Grantham
• 1831: Special Constable Act created
• 1833: Coldbath Fields Riots (Grays Inn Road), handled with the use of force. PC Robert Culley was killed and the jury returned a verdict of Justifiable Homicide
• 1837: Bow Street horse patrol was transferred to the Metropolitan Police
• 1838: Bow Street Runners and Marine Police absorbed into the Metropolitan Police
• 1842: Formation of the Detective Department
• 1846: Plain clothed officers used frequently by this time
• 1848: 150,000 special constables were sworn in for handling Chartist Demonstrations
• 1858: First police van for transporting prisoners, called Black Marias
• 1870: Standard height requirement for officers set to 5ft 8in (except Thames Division, 5ft 7in)
• 1872: First police strike
• 1877: Trial of force detectives exposes internal corruption
• 1878: Detective Department was renamed the CID
• 1879: Rules established for dealing with murder cases
• 1886: Started training of horses for controlling disorderly demonstrations
• 1887: “Bloody Sunday” riot on 13th November - Trafalgar Square
• 1888: Jack the Ripper murders
• 1890: Opening of new offices known as New Scotland Yard
• 1895: Height restrictions raised to 5’9”
• 1898: Calls for officers to be armed with revolvers following assaults and the murder of a PC
• 1900: Construction of a floating police station at Waterloo Pier
• 1901: First police photographer employed
• 1901: Fingerprint Bureau formed
• 1902: First conviction by fingerprinting
• 1905: First murder conviction by fingerprinting
• 1907: 13 February, clash between police and 800 Suffragettes outside House of Commons
• 1910: Dr Crippen arrested with the aid of radio telegraphy and forensics
• 1912: First recorded conviction with ballistics evidence
• 1914: Women police founded
• 1915: London Ambulance Service commences operation