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Phoenix Caisson in Kent Designated - Part of the Mulberry Floating Harbour Used in the D-Day Landings

The Phoenix caisson, a rare and poignant reminder of the Mulberry 'floating' Harbour which played a major role in the success of the D-Day landings in June 1944, has been scheduled by the Department for Culture Media and Sport on the advice of English Heritage. It has been added to the National Heritage List for England as an Ancient Scheduled Monument.

Phoenix Caisson off the coast of Littlestone-on-Sea, Kent. The huge concrete structure was part of the Mulberry Harbour plan to create landing stages in France to support the D-Day invasion.
Phoenix Caisson off the coast of Littlestone-on-Sea, Kent. The huge concrete structure was part of the Mulberry Harbour plan to create landing stages in France to support the D-Day invasion. © Historic England

It is a large concrete structure that survives remarkably intact and is visible at low tide off Littlestone-on-Sea in Kent. It is one of only six known examples of Phoenix caissons in British waters. The others can be found in Portland Harbour, Dorset, (two caissons listed Grade II) Shoebury Ness, Essex, (scheduled) Langstone Harbour, Portsmouth and off Pagham, West Sussex.

The Phoenix caisson was built in 1943-4 as a floatable breakwater component of the Mulberry Harbour which was considered to be a major technological and engineering achievement. It was effectively a mobile port facility, designed to sink or float as necessary, and was used by the Allies to land troops and arms at Normandy as part of Operation Overlord.

Phoenix Caisson off the coast of Littlestone-on-Sea, Kent. The huge concrete structure was part of the Mulberry Harbour plan to create landing stages in France to support the D-Day invasion.
Phoenix Caisson off the coast of Littlestone-on-Sea, Kent. The huge concrete structure was part of the Mulberry Harbour plan to create landing stages in France to support the D-Day invasion. © Historic England

Its location, stuck in sand and silt on the sea floor off Littlestone-on-Sea illustrates the logistical problems involved in the invasion, as it remains where it was 'parked' prior to D-Day after it proved impossible to re-float and tow it across the English Channel.

Veronica Fiorato, Designation Team Leader for English Heritage in the South said: "The Phoenix caisson is a tangible reminder of Operation Overlord and its vital contribution to British and world history. It has stayed exactly where it was parked during the Second World War and survives in very good condition, having lost only its anti-aircraft gun mounting."

U.S. Army vehicles roll ashore on one of the floating causeways of the 'Mulberry' artificial harbour off 'Omaha' Beach, 16 June 1944. The causeway had been erected by U.S. Navy SeaBees. Source - Army Signal Corps Collection in the U.S. National Archives.
U.S. Army vehicles roll ashore on one of the floating causeways of the 'Mulberry' artificial harbour off 'Omaha' Beach, 16 June 1944. The causeway had been erected by U.S. Navy SeaBees. Source - Army Signal Corps Collection in the U.S. National Archives.
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