In March 1909 the Port of London Authority came in to being based on an act of Parliament made the previous year.
The PLA is a self-funding public trust that was established to govern the Port of London (as was) and to manage and maintain the tidal part of the river Thames. It looks after about 95 miles of river from Teddington Lock out to the North Sea off Southend and has responsibility for the safety and security of the river and its users.
These tasks include controlling the safe navigation of river users, keeping the Thames safe for navigation and the promotion of Thames as a transport route.
In fact the Thames through London is the busiest inland waterway in the UK for freight operations (over 5 million tonnes in 2013) and also sees significant numbers of passenger journeys on river buses, sightseeing boats and cruise ships.
To help deliver the diverse range of responsibilities the PLA has a varied fleet of vessels. These include various boats used by the Harbour Masters to enforce the rules and regulations of the river and manage safe navigation.
The PLA is also responsible for the production of river charts to and has its own hydrographical survey vessels that map the river bed along with boats designed to collect floating debris to keep the river safe for use.
There are also workboats that maintain mooring buoys and other river facilities that are all required to help maintain the river Thames as a working river for both commercial and recreational users.
Hookness – Maintenance vessel
PLA Diver – Diver support boat
A few more pictures can be seen here.