Garlieston's Secret War: the development of the Mulberry Harbours and the men who made it happen

The WWII D-Day Mulberry Harbour trials around Garlieston

Mulberry Harbour Garlieston: as testing nears completion, a Crusader tank heads away from Cairn Head (Portyerrock, nr Garlieston) on Allan Beckett’s floating roadway.
Picture: H30929 © IWM

Garlieston enters the Mulberry Harbour story in the autumn of 1942. Several locations in this remote Wigtownshire village including Garlieston Harbour, Rigg Bay and Cairn Head were used for evaluating three prototypes in preparation for the D-Day invasion. Brigadier Sir Bruce White wrote:

It was necessary to test the components for the artificial harbours. I tried out any proposal, whether it was made by my own staff, by another Service or even by individuals. A testing site had to be found in the UK for these trials. A search of various areas resulted in the selection of a location in the Solway Firth where the rise and fall of the tide — about 24 feet — was similar to that off Normandy. It was also subject, at times, to very rough seas. Above all, however, its remoteness from London decided the issue, as interested visitors were reduced to the minimum. Police protection was provided, when I approached the Scottish authorities, and a small unit was established at the experimental site.

Garlieston Mulberry Harbour trials: Major Carline, Major. Steer-Webster, QMG Thomas Riddell-Webster, Brigadier Sir Bruce White arriving at Garlieston Harbour, 13th March 1943
Major Carline, Maj. Steer-Webster, QMG Thomas Riddell-Webster, Brig. Bruce White
arriving at Garlieston Harbour, 13th March 1943 (© IWM)
Churchill takes a personal interest in the Mulberry Harbour project
14th May, 1943

The first appearance to us of any military working party was on Friday the 14th inst., when they entered without any formal notice or warning to the estate, in a military truck, via Breakwater Lodge and the shore path, to Rigg Bay, and started work in the Bay. On Saturday last, 22nd inst., they resumed operations, and also put notices at certain places, and patrolled the shore path from approximately Breakwater Lodge to the Cruggleton Lodge, and turned all intruders away from that area. Our old notice board at Breakwater Lodge gate, which reads “These grounds are strictly private” has now got nailed underneath it to the same post, two fresh boards, printed –


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The Prototypes

Brigadier White’s Transportation 5 Department (Tn5) at the War Office was tasked with evaluating three Mulberry Harbour prototypes at Garlieston.


Designer: Hugh Iorys Hughes

A series of initially floating caissons linked by an elevated roadway. Sunk into position by flooding. Discarded because shifting sand beneath the settled caissons caused instability and being a fixed installation could not be in use around the clock.

Garlieston Mulberry Harbour trials: Hippo caissons and roadway at Rigg Bay, Garlieston

Swiss Roll

Designer: Ronald Hamilton, Department of Miscellaneous Weapons Development

A canvas roadway with hinged side ‘flaps’ that prevented water ingress when under load. Initially promising but prone to flooding with heavier loads. Some rolls were used during the D-Day invasion to disembark troops from landing craft.

Garlieston Mulberry Harbour trials: Lorry tries out Swiss Roll off Cairnhead nr Garlieston

Spud Pier and ‘Whale’ Roadway

Designers: Lobnitz & Co., Renfrew; Lt. Col. William Everall and Major Allan Becket, Transportation 5 (Tn5)

A floating pierhead that could be elevated on legs for stability and to avoid harsh sea conditions linked to an innovative floating roadway. This was the harbour that went to war.

Garlieston Mulberry Harbour trials: Spud pier and floating Whale roadway off Cairnhead nr Garlieston

The harbour that went to war

The Spud pier combined with the floating roadway, codename WHALE, enabled the piers to be used at all states of the tide.

The pier could be jacked up so that it was no longer afloat to provide a stable berthing platform and included innovations such as the ramp that enabled Tank Landing Ships (LSTs) to be run ‘aground’ for discharging via the bow doors. Some piers also featured an elevated platform so that vehicles could also be discharged from the top deck.

An LST is nudged towards a beaching ramp (433)

Thanks to an innovative spherical bearing, sections of the floating roadway could oscillate through a wide range with respect to their neighbours. The addition of one or more telescopic bridge spans mean that the angle of the roadway could adjust to changes in water depth or the raising or lowering of the adjacent pier.

The floating roadway, designed by Allan Beckett, is given a severe test off Cairn Head.

Tank Landing Ship comes alongside
a prototype pierhead

Sheltered Water

All harbours need to provide a sheltered anchorage. And so it was with Mulberry.

Like all other components the shelter would also need to be transported across the English Channel. A three pronged approach was devised: blockships, bombardons and phoenix caissons.

Blockships were just that, 60 retired merchant vessels and warships that undertook a final voyage from Scotland before being sunk and filled with sand within sight of France. Line astern they formed a formidable sea defence and even before the artificial port was operating, vessels were unloading men, ammunition and supplies on to amphibious craft in their lee.

Bombardons were massive steel structures, cruciform in section, that were anchored at the outer reaches of the harbour. Their profile and their ability to oscillate meant they were able to absorb wave energy, effectively acting as tethered dampers rather than a rigid barrier.

Phoenix caissons were colossal, reinforced concrete structures, weighing up to 6000 tons, that were flooded once in position and when aligned formed a massive concrete wall. More than 213 of all types were built all over the UK.

A Phoenix being towed to its assembly point. On reaching the Normandy shore
sea cocks on each section were opened, and the caissons settled on the sea floor

D-Day June 6th 1944

To construct our defences we had, in two years, used some 13 million cubic meters of concrete and 1.5 million tons of steel. A fortnight after the landings by the enemy, this costly effort was brought to nothing because of an idea of simple genius. As we know now, the invasion forces brought their own harbours and built at Arromanches and Omaha, on unprotected coast, the necessary landing ramps.
Albert Speer – Reich Minister of Armaments and War Production for Nazi Germany

Tank Landing Ship with bow doors open docked at Mulberry “B”

The Storm

On June 19th, 1944, a savage and prolonged ‘once in 40 years’ storm struck the Mulberry Harbours. The American harbour — Mulberry A — was completely destroyed. The British harbour — Mulberry B (“Port Winston”) — narrowly survived. We now know that the American harbour was subjected to waves that were significantly larger than those experienced at the British harbour. In both cases the waves exceeded what the harbours were designed to withstand.

MULBERRY “B” actually did far more than the job for which it was intended, despite storms of intensity far beyond that for which it had been designed and despite the total loss of its deep water breakwater, is the success story of a military and naval operation unsurpassed in the history of warfare.

From the time it was put into operation, four days after D-Day until the 31st of October, 1944, 628,000 tons of supplies, 40,000 vehicles and 220,000 troops were put ashore in the sheltered area afforded by MULBERRY “B”. Expressed in another way, 35% of the British stores, 17% of the British vehicles and 23% of the British personnel were landed inside the Mulberry.

From D plus 4 on it had been planned to handle 6,000 tons of stores a day at MULBERRY “B”, actually, however, from the 20th of June to the 1st of September the port averaged 6,765 tons a day.

– Major General R W Crawford USA

The US Mulberry was dubbed “A” and the British “B”.


Roy Walter
Online production
Brook House Limited
Picture credits
Imperial War Museum (IWM)
The unflagging efforts of Mrs Jane Evans of Penkiln Farm, Garlieston, in highlighting Scotland’s role in the development of the D-Day Mulberry Harbours.
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