The force was originally formed in 1909 as the Port of London Police following Parliament's passing of the Port of London Authority Act 1908 on 21 December the previous year.

[3] Eight of the force's officers drowned in the docks between 1913 and 1951, with other fatal casualties from being run over by a train, crushed under part of a ship's cargo and falling into a dry dock.

The docks were badly hit during the Blitz and PC Robert Charles Winney and Sergeant Charles Edward Showell received posthumous King's Commendations for Brave Conduct in Civil Defence after being killed by an unexploded bomb on the night of 18-19 September 1940.

Generally they are only worn by uniformed officers, below the rank of Inspector.

[12] A port constable may, within the port premises, enter and search a vessel or vehicle if he, with reasonable cause, suspects that he might find anything which has been stolen or otherwise unlawfully obtained:[12] A port constable may seize anything found on board the vessel or in the vehicle which he with reasonable cause suspects to have been so stolen or obtained unlawfully.

[14] A constable may detain a person who, after being warned by an officer of the Port Authority not to do so, gets on to, or remains, on a movable bridge belonging to the Port Authority, when it is about to be moved, or is being moved, or before it is properly closed and fastened, if that person's name and address is unknown to and cannot be ascertained by the constable.