The force was originally formed in 1909 as the Port of London Police following Parliament's passing of the PLA Act on 21 December the previous year. The PLA took over control of all London's commercial docks from three separate private companies - the London and India Docks Company (running London Docks, St Katharines Dock, Tilbury Docks, Royal Albert Dock and Royal Victoria Dock), the Surrey Commercial Docks Company and the Millwall Dock Company. Each of those companies had had its own private police force to police its docks and these were merged to form the new PLA Police, with jurisdiction in the docks themselves and within a mile of them. Additionally Thames Division of the Metropolitan Police had originally been founded in 1798 as the Thames River Police to police shipping in the Pool of London.