Port of London Authority (PLA) was established in 1909 to bring order to the chaos and congestion that prevailed on the Thames. On 31st March 1909 the PLA assumed power and responsibility for the enclosed docks, the conservation of the river for 70 miles downriver of Teddington Lock, and for the registration of watermen and lightermen, and their craft. Following WW1 the new PLA Head Office in Trinity Square was opened by Prime Minister Lloyd George on the 17th October 1922.

In June 1959 the PLA launched its Thames Navigation Service (TNS). Radar and VHF radio enabled the Operations Room, at Gravesend, to monitor and direct shipping on the river. Trade through the Port, particularly the enclosed docks, reached its peak in 1964 at 55 million metric tonnes. The PLA closed the London and St Katharine's Docks in 1968. The small East India Dock had closed in 1967. The Royal Docks were closed at the end of 1981.

The PLA opened its new £3 million main office, London River House, next to the Port Control building, at Gravesend in 1992. The sale of Tilbury Docks in 1992 ended the PLA's link with cargo-handling. Today the PLA's role is to help people use the river safely - whether it is for deep-sea trade, river borne freight within London, commuting, sailing or rowing.