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Port of London Authority (England)

Last modified: 2020-10-03 by rob raeside
Keywords: london | port of london authority | pla | conservators | thames conservators | thames powder flags |
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[Logo of Greater London Authority] image by Graham Bartram (

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Description of the flag

The House flag comprises of the banner of St George bearing in the centre thereof the P.L.A. arms within a yellow-edged red annulet inscribed "Port of London Authority" in yellow lettering. The arms look quaint; they consist of a representation of St Paul - The patron saint of London - encamped up to his waist in the Tower, holding in his right hand a drawn sword and in his left hand a yellow scroll, all on a light blue background.
Martin Grieve, 12 July 2009

The "Port of London Authority house flag", as shown by Graham Bartram, is a St. George's cross, with Port of London Authority seal over it.
The Port of London Authority (PLA) is a "public trust" established in 1908, as the port and navigation authority for ninety-five miles (150 kilometres) of the tidal Thames from the sea at Southend-on-Sea in Essex to Teddington. However, there are extensions seaward to its responsibilities within the London Pilotage District, including the main approach channels to the Thames. It also has a number of other conservancy functions, some of which are shared with the Environment Agency of the UK Government. Upstream of Southend-on-Sea, the PLA is also the majority owner of the river bed and foreshore to the mean high water mark. The other main owner is the Crown Estate.
The PLA web site states that London is one of the top three ports in the UK and handles over fifty million tonnes of cargo each year, with more than seventy independently owned and operated port facilities in its jurisdiction. There are also a large number of yachts and other pleasure craft used on the River Thames. Governing law is the Port of London Act 1968, as amended.
(1) Port of London Authority, web site,, consulted 24 September 2006
(2) Port of London Act 1968 as amended, consulted Port of London Authority, web site,, updated to 05 January 2006, consulted 24 September 2006
Colin Dobson, 25 September 2006

Harbour Master flag

[Port of London Authority, Harbour master] image by Colin Dobson, 25 September 2006

At Greenwich on Saturday, I saw a Harbour Master's boat, flying the PLA blue ensign, and also (from the centre of the boat) a blue flag with the words "HARBOUR MASTER" on two lines in white.
Jonathan Dixon, 24 September 2006

I have also seen this flag many times on the Thames. Source: Personal observation, circa 1980 to date. As I recall, this flag is one-sided only.
Colin Dobson, 25 September 2006

19th Century Flags

[Port of London Authority, 19th Century] image based on Bartram (2004) by Martin Grieve, 6 August 2006

Described as a 19th Century flag, The Port of London Authority was established in 1909 and was entrusted with the duty of making good any deficiencies in the port's accommodation, equipment and service both for ships and goods; to carry out all conservancy duties over sixty-nine miles of the tidal Thames and exercise the powers hitherto vested in the Watermen's Company relative to the registration and licensing of craft and boats as well as lightermen and watermen.
Jan Mertens, 20 February 2005

From "British Flags and Emblems" by Graham Bartram, I have drawn the Ensign of the Port of London Authority. Please note that this British flag has changed [see below for rendition of earlier version], although I am unsure as to the exact date. Recently, on the Discovery channel on TV, there was a documentary about this governmental department, and the flag depicted had what I presume can only be the older version with a more complicated sea-lion in the fly. Please refer to Campbell and Evans "The book of flags, fifth edition, 1965" page 49, which shows the reader what the badge defacement is (or was?) in black and white.
I quote from the above-mentioned source:

"The Port of London Authority, which controls the mighty traffic of the great London Docks, has two different flags ... The blue Ensign flown by P.L.A. vessels on service in the docks or on the Thames is defaced in its fly by a gold sea-lion grasping a trident" Perhaps then, we have another example of flags being replenished with the newer version as current stock becomes worn and/or threadbare?
Martin Grieve, 6 August 2006

Earlier version of the flag: PLA ensign 1911-c1999

[Port of London Authority, 19th Century] image by Martin Grieve, 12 July 2009

The original badge [see detail below] is depicted in black and white in "The book of flags" by Campbell and Evans (1953 & 1966 editions). It is a rather more attractive emblem than that depicted in the Admiralty flag book of 1916. I don't know for certain when the badge was simplified, but a great many British defacements underwent a face-lift in 1999, so that date may be the correct one.
Some more information on this flag and the house flag (illustrated by Graham Bartram) from EMC Barraclough's Flags of the World, 1965: "Familiar on the River Thames from Twickenham to the Nore are the Ensign and the House flag of the Port of London Authority - often referred to as the "P.L.A."
These two flags are worn by virtue of an Admiralty Warrant dated 25th November, 1911. The first mentioned is the Blue Ensign defaced with the badge of the Authority - A sea-lion grasping a trident in yellow - in the centre of the fly.
Martin Grieve, 12 July 2009

Detail of badge: PLA ensign badge 1911-c1999

[Port of London Authority, 19th Century] image by Martin Grieve, 12 July 2009

Pennant of the Chairman of the Port of London Authority

[Port of London Authority, Chairman's pennant] from Port Cities, located by Jan Mertens

Pennant of the Chairman of the Port of London Authority with a rope and two Inglefield clips attached. The Port of London Authority was established under the Port of London Act in 1908. Pennant by Porter Brothers & Co. Ltd.
Jan Mertens, 20 February 2005

The P.L.A. Vice Chairman's pennant is shown on page 80 of "British flags and emblems" by Graham Bartram but the 2 diagonal bands with writing on them - namely (from hoist) FLOREAT IMPERII and PORTVS on Graham's illustration are shown "per bend sinister", whereas on the photograph they are "per bend". Which is correct?
Martin Grieve, 23 June 2007

Flag of the Conservators of the River Thames

[Thames conservators] image by Martin Grieve, 4 February 2008

1857. An Act of Parliament created the Thames Conservancy. It was responsible for maintaining the river in a navigable condition from the Estuary to a point just east of Windsor at Staines, where the Thames Valley begins. This had previously been done by the Corporation of the City of London.

1866. Another Act made the Conservators responsible for the river between Staines and the head of navigation at Cricklade, near Swindon.

1874. The flag of the Conservators, which was flown on their launches, appeared in the Hounsell Flag Book; a 1:2 St George's flag with the seal of the Conservators in the centre. The seal included the Arms of both the City of London and Trinity House, the corporation responsible for coastal navigation. Officials authorized by the Conservancy to regulate traffic at such events as regattas fly a simpler flag bearing the words 'Thames Conservancy' one above the other on a red field. When the Conservators are on board, however, the flag displaying the arms is flown at the stern while at the bows is a pendant bearing the St George's cross and the letters 'T.C.'. (Evans, "The Book of Flags")

1908. A new organisation, the Port of London Authority, was created and took over the tidal river below the lock at Teddington, West London. The authority adopted a flag similar to that of the Conservators, with its seal in the centre of a St George's flag, though in this case the flag was square.

1974. The Conservancy became a division of the Thames Water Authority and its flag is no longer used.

David Prothero and Martin Grieve, 4 February 2008

Thames Powder Flags

[Thames Powder Flag 1]     [Thames Powder Flag 2] images by Pete Loeser, 29 September 2020
based on these drawings found in the "British Empire. Badges of Public Departments & Admiralty Board of Trade."

Thames Powder Flags were red squares with either one crown, or two crowns side-by-side. They are shown in the Admiralty Flag Books of 1907 and 1915, and also George Philip's "Flags of all Nations" folded flag sheet of the late 1930s. The Mayor of Rochester was, by ancient Charter, Admiral of the Medway and may have instituted a similar flag for that river. It might be worth contacting Medway Council, or Kent County Council archivists.
David Prothero, 8 January 2007

[Thames Powder Flag 1] speculative image by Pete Loeser, 29 September 2020

In the 1960's. I served aboard a Naval Armament Vessel, carrying explosives between Royal Naval Armament Depots. While embarking or discharging cargo, we exhibited the International Code Flag 'Bravo', which of course was a red flag. However, before its closure in the 1960s, when we were on passage on the River Medway (Kent, England) to and from Upnor Armament Depot, we had to display a square red flag with three crowns (in a triangle) in the fly.
Peter Billing, 7 January 2007

According to a publication printed under the authority of His Majesty's Stationery Office by Eyre and Spottiswoode Ltd, London, entitled "British Empire. Badges of Public Departments & Admiralty: Board of Trade" these first two flags came in two sizes: 6x6 foot and 4x3 foot. (sourced above)
The third drawing is completely speculative based on Peter Billing's description using the same King Edward style crown and assuming the triangle faced upward.
Pete Loeser, 29 September 2020