Mulberry Harbour Phoenix Units, Portland

The Portland Mulberry Harbour Phoenix Units are two reinforced concrete caissons, built as part of the artificial Mulberry harbours that were assembled as part of the follow-up to the Normandy landings during World War II. Out of a total of 148 produced units, two units still remain at the Isle of Portland, Dorset, England. They are situated approximately 115 metres north of Castletown Pier, date to 1944, and are approximately 60 metres long, 20 metres wide, and 15 metres high. Each weighs 7,700 tons. Portland's two units became Grade II Listed in May 1993.

History
When planning the invasion of France the allies were extremely worried that they would be unable to supply the troops who were ashore. The only reliable method of landing large quantities of resources was through a major port. As the German army held all of France's harbours, the solution was the Mulberry harbours, and two temporary harbours, each the size of the port of Dover, were built of prefabricated sections in Britain then towed to Normandy in the wake of the invading armies. In a ferocious building program the pieces were put together on the beaches of Normandy, creating two operational harbours within two weeks.

Facilities all along the south coast of England were used to construct the various elements needed for the harbours, and nine of the Bombardons (61m long cruciform steel floats) were assembled in Portland Harbour. The Bombardons were designed to be moored seaward of the main Mulberry structure formed by Phoenix breakwaters. Records in the National Archives showed that the units made in Southampton Docks were then tested in Portland Harbour after completion. These Phoenix caissons were left moored at Portland in 1944, sunk for concealment from the enemy, before being raised and towed to France. Although most of the temporary harbour units were towed across to serve the D-day landing of 6 June 1944, several Phoenix breakwaters are still in use in Britain today; two of which are part of Portland Harbour.

Following the war, ten of the units were towed back to Portland Harbour, and these remained within its harbour after the war for several years, which provided protection for the construction of a new pier - Queen's Pier (often known as 'Q Pier'). Due to the size of the units, as well as the lack of salvable material, most Phoenix caissons remain where they were planted during the war. The ones towed back to Portland were intended to be retained permanently in the harbour, to create an inner harbour that could be used for berthing the latest, large Royal Navy Battle Class destroyers. The Liverpool Echo reported this on 23 September 1947. The First Sea Lord, Admiral Sir John Cunningham, inspected progress on this new Inner Harbour during a visit to Portland on 14 October 1947.

However in 1953 eight of the spare units stored at Portland were offered by the Admiralty to the Netherlands to repair and block breaches in the dykes, following the great storm of January 1953. The violent storm in the southern North Sea had occurred overnight on 31 January/1 February 1953, and had caused severe flooding in southern England and particularly the Netherlands, where it was reputed to have been the worst flooding for 300 years. On 20 May 1953 the Dorset Daily Echo reported that the British Admiralty had put eight of the units at the disposal of the Dutch Authorities, and as such they were to be raised for a third time in nine years and towed to Holland to form defences against future dangers from North Sea floods.

By 17 July 1953 six of Portland's units had been towed by Dutch tugs to the Zeeland province, although the other two caissons ran aground and had to be abandoned. One of these had gone aground in bad weather at the Ooster Schelde, and the other ran aground, and remained flooded. This was the last movement of any units Phoenix caissons in the world. Of the six units successfully towed from Portland, four now form the buildings of a museum dedicated to the 1953 event.

Although eight of Portland's units were removed for this event, the two remaining units left behind became permanently moored. The two sections are appropriately sited in Portland Harbour as a reminder of the remarkable enterprise. The role of the two units still situated in Portland's harbour is as a wind brake, which helps ships berth at 'Q Pier' in the harbour.