by Ken Ford
Maj Hasler was immediately attracted by the scheme. He realized at once that his canoes could approach the ships unseen if they could get in close enough to attack. He spent the day studying the problems associated with travelling up the river to Bordeaux, the tides, the moon phases and the enemy opposition. By the end of the day he had arrived at the makings of a practical solution: the cockles could be transported to the mouth of the river by submarine at night, then paddled the 60 miles upriver in stages – moving by night and lying up by day – ready to attack the enemy ships in Bordeaux with limpet mines under the cover of darkness. Escape could be arranged by moving back downriver, if possible, or overland if not, to a rendezvous point with a submarine a few days later.
That evening he discussed his scheme with Col Neville. The Chief Planning Coordinator agreed with the basic outline plan that Hasler had sketched out. If successful, such a mission could be the solution to a problem that had been causing disquiet to the government at the highest level for some time. Hasler was now asked to formulate a detailed operational plan for Frankton with the planners at Combined Operations, which could be put before a meeting of the whole COHQ and the Combined Chiefs of Staff Committee for approval.
Hasler returned to Southsea in a state of high excitement. His unit now had a purpose and a definite objective towards which their training could be focused. For security reasons the method of the attack and its objective had to be kept secret from the whole of the team during the preparation stages. There would have to be a sharp ramping-up of development and familiarization work on the new Cockle Mk II, but there now seemed, at last, to be a specific goal in sight and a clear objective to work towards.
Steps leading to the beach from the esplanade at Southsea close by the RMBPD base. Lumps Fort can be clearly seen in the background. The beach has been raised since the war with the deposit of large amounts of shingle; in 1942 the wall was 4ft higher than today. To maintain fitness and initiative, Maj Hasler forbade the use of these steps, so boats, cockles and equipment all had to be manhandled up and down the 8ft-high wall like an obstacle course. (Ken Ford)
Hasler’s outline plan now had to be converted into a detailed operational scheme, capable of convincing those in authority that it was worth the risk and had a high chance of success. To ease his burden, Hasler took his second-in-command, Capt Stewart, into his confidence and the two of them set about gathering all the background information required for the plan from a variety of sources. While the two officers concentrated on the project the rest of the unit undertook a new range of tasks specifically geared to the raid.
The War Diary for the RMBPD shows the changes in the type of activities undertaken after Hasler’s 21 September meeting with the CO planners. On the 27th of the month normal working hours were rearranged to allow for more night training. Both No. 1 and No. 2 Sections worked from 0830–1330 hours, then each section would work alternate nights from 1900–0500 hours. Most days included canoe work, especially during rough weather conditions, as familiarization with boat handling in heavy seas was crucial. On 9 and 10 October the diary shows that the sections practised both silent approaches and stalking sentries, along with the stripping and assembling of weapons in the dark. Two days later they were weightlifting at sea from canoes! On 17 October Hasler lectured on dockyards, and further compass training was also given to the unit. By 24 October more specific training for the operation was also initiated, with the marines erecting iron plating to represent the sides of a ship and practising placing limpet mines. On 30 October, No. 1 Section, the group Hasler had selected for the operation, went north to Scotland to join the submarine depot ship HMS Forth to continue the training specific to Operation Frankton. As a cover to protect the secrecy of the planned operation, however, the move was described as being for practice in advanced training techniques.
In the meantime Hasler and Stewart worked on finalizing their plan, as well as working with SARO on the finer details of the Cockle Mk II, which was so essential to the operation. Prototypes were available to the unit, but some further modifications were still required. The final design was a 16ft-long craft with a beam of 28 inches. Its depth, when erected and in use, was 11 inches, but the cockle could be collapsed to just 6 inches by moving eight hinged struts when the craft was out of the water. It was built of plywood and covered with canvas and rubberized fabric. Its flat plywood bottom was reinforced with several wooden runners along its length, which allowed it to be dragged over rough ground without any damage. The two-man cockpit was covered with a watertight rubberized cover with two circular openings allowing access for the canoeists. The men were to wear camouflaged waterproof anoraks with elasticized bottoms that fitted snugly over the circular openings to prevent water entering the cockpit. A small breakwater on the foredeck helped deflect any water that hit the forward end of the craft.
A vital addition to the craft was a magnetic compass with luminous markings mounted just in front of the lead canoeist (navigating the cockles on the correct bearing in the dark was a vital aspect of the training programme). Propulsion was by means of long double-ended paddles. Each was made from two single paddles jointed at the centre point and designed so that one blade was at right angles to the other, so that when one blade was in the water thrusting the canoe forward, the other was at right angles to the motion producing little wind resistance.
The Cockle Mk II sat low in the water, making it particularly inconspicuous. However, when its crew were paddling at speed with their oars rising and dipping it became less so. If there was any danger of being observed by the enemy, the crew would split the paddles and continue with just a single paddle in use, crouching low in the cockpit to reduce their silhouette. With its very narrow sleek design and the smooth actions of very accomplished oarsmen, the Cockle Mk II could cut through the water swiftly, silently and hopefully almost unobserved.
By the end of October the final design of the Cockle Mk II had been agreed and the craft were in production. Now that the unit had its canoes the means of deploying them had to be developed. Launching a canoe at sea from a ‘mother ship’, most likely a submarine, was a difficult task. The very lightness of the canoe meant that when empty it did not sit well on the water. Trying to load stores and men into the flimsy craft as it rose and fell with the swell before it was swamped was fraught with danger. Ideally a method had to be devised to launch the cockle fully loaded with its cargo and crew straight into the sea.
An ingenious solution to the problem was developed by using the deck gun of a submarine as a crane. A long steel girder was clamped to the barrel of the gun from which a wood and canvas sling was attached. The fully loaded cockle, complete with its crew and stores, was placed into the sling and hoisted over the side and into the water. The sling’s movement was controlled by means of the gun’s transverse and elevation systems. Hasler’s contribution to the design of the cockle had ensured that the craft had sufficient longitudinal strength to withstand the stresses of being hoisted fully loaded in this way.
By the last week in October Maj Hasler had devised a final scheme for the operation. He had obtained sufficient intelligence on the topography of the Gironde estuary, the River Garonne, the likely enemy defences, the state of the moon and tides, and on the location of the blockade busters in Bordeaux to build a workable plan. Aerial photographs and detailed maps showed the possible sites at which the canoes could hide during daylight hours and the stretches of river that could be navigated at night. The maps were colour-coded to show areas that were occupied by the enemy, those that might be dangerous and those that appeared to be safe.
The operation would be undertaken by six men in canoes, one officer (Hasler) and five other ranks selected from No. 1 Section of the RMBPD. It was believed that sufficient limpets for the destruction of six enemy ships could be carried in just three craft. The passage to the mouth of the Gironde would be by submarine and would take place in the dark phase of the moon at the beginning of December. The canoes would be launched s
oon after nightfall to allow the maximum time of darkness for them to pass the German seaward defences, the small naval base at Le Verdon and to enable them to get well into the river before daylight.
Maj Hasler and Capt Stewart put a Cockle Mk II through its paces in the calm seas of the Solent. Capt Stewart was Second-in-Command of the RMBPD and took charge of the unit while Hasler was in France during Operation Frankton. (Royal Marines Museum Collection)
Men of No. 1 Section RMBPD practise their rowing techniques in a whaler off Lumps Fort at Southsea. Several men who took part in Operation Frankton have since been identified: extreme left is Cpl Laver; immediately in front of Laver is Marine Ewart; extreme right is Sgt Wallace and behind Wallace, second from the right, is Cpl Sheard. (Royal Marines Museum Collection)
It was intended that the move upriver would take three days, with the attack on the blockade ships taking place on the evening of the fourth day. Each night, under the cover of darkness, the cockles would paddle their way upriver, covering between 15 and 20 miles per night. The state of the tides would mean that not all the nighttime hours could be used effectively. If the current against them was too great they would have to seek shelter and wait for the tide to turn. Before light, a place for them to rest up would have to be located and the craft pulled out of the water and camouflaged. Once daylight came, the most nerve-wracking part of the journey had to be endured, for the men and their equipment would have to remain silent and unobserved throughout the whole of the day, possibly in fairly close proximity to the local population. The attack on the ships would take place in darkness during the early part of the evening so as to give the maximum time for the escape downriver before dawn. Each of the craft would plant limpets to a prearranged plan. After carrying out the attack, the cockles would move downstream to a point on the northern bank of the River Gironde, where the boats would be scuttled and their crews would make their escape.
Permission had been granted by the Royal Navy for the use of a submarine to carry Hasler’s team to their launching point. However, there was one major drawback. The use of submarines was under strict control, as they were in demand for use by other units for covert operations or rendezvous. Hasler was told that his party could join HMS Tuna on the River Clyde in Scotland and disembark with the submarine on her next normal patrol in early December. As the patrol was destined for the North Atlantic, the route could be made via the Bay of Biscay to take in the requirements of Operation Frankton. There was, however, a particularly bad piece of news for Hasler to digest as well. He was told that it would be impossible for the submarine to return approximately a week later to pick up his group, as the risks were too great. By then the enemy defences would be on high alert looking for just such a rescue attempt. There was also a practical problem, for the chances of a submarine finding small dark canoes on a pitch-black night miles out to sea were negligible. Escape would have to made overland through Spain to Gibraltar.
Waiting and watching for any British attack around the River Gironde were troops of all three German services. This part of south-western France was garrisoned by the German 708th Division, a two-regiment static formation raised in the Strasbourg area in 1940. Two armed trawlers maintained a permanent patrol off the mouth of the river and were often joined by other trawlers on inshore minesweeping duties. Just inside the river on the south bank was the small port of Le Verdon, a base for a flotilla of six M-Class minesweepers. Most of the anti-aircraft defences in the area were manned by Luftwaffe personnel and these were grouped around the city of Bordeaux and at Le Verdon. Facing the sea to the south of Pointe de Grave were two medium coast defence batteries, one of six guns near Royannaiss and another emplacement of four guns closer to the lighthouse on the point. Several searchlight batteries covered the estuary and the first few miles of river upstream of Le Verdon. At Soulac-sur-Mer, four miles south of Pointe de Grave, was a seaward-facing radar station.
On 29 October Hasler’s plan was put before the Executive Committee of COHQ in a meeting chaired by Lord Louis Mountbatten. The plan was approved unanimously with one major change; Mountbatten thought that the number of canoes should be increased from three to six in case of unforeseen accidents. The question of who was to command the raid was also raised. Mountbatten was reluctant to risk a senior officer crucial to the development of small boat tactics on such a dangerous operation. Hasler was reportedly distraught at the news and pleaded his case for going. He reasoned that he could never accurately develop raiding techniques and equipment if he had never participated in a raid. Moreover, he was loath to send his men on an operation without being there to guide them. ‘If the raid was a failure,’ he commented, ‘how could I ever face the other men in the unit?’ Mountbatten put the decision to the executive and sought the views of the other officers around the conference table. All except Col Neville felt that Hasler should not lead the raid because of his significance to his work with the BPB. Nonetheless Mountbatten, moved by Hasler’s passion and commitment, relented. ‘Against my better judgement,’ he said with a smile, ‘I’m going to let you go.’
A few days later final approval was granted by the Chiefs of Staff Committee when Hasler was already back in Scotland working with Lt Mackinnon and the No. 1 Section. They were on board the depot ship of the 3rd Submarine Flotilla anchored in Holy Loch, HMS Forth, carrying out their final training on the attack phase of the operation. The flotilla’s commander, Capt Ionides, had already been informed that he would have the final say in whether the operation went ahead and Hasler had to prove to him that the unit was fully trained to fulfil the mission’s objectives. The submarine carrying the party, HMS Tuna, was due to sail on her patrol on 30 November. By that time Ionides had to be convinced that the men were ready.
A box of coloured glass ampoules containing various concentrations of acetone of the type used in a limpet mine fuse during the raid. The strength of the liquid inside each ampoule determined the rate at which a celluloid washer in the mine’s fusing mechanism would dissolve to release the spring-loaded firing pin and ignite the explosives. (Courtesy of Richard Wooldridge, Combined Military Services Museum)
After No. 1 Section’s arrival in Scotland on 30 October, training proceeded at an intense pace, with their departure for France planned for a month’s time. Further training was dedicated to the use of the magnetic limpet mine. The mine was designed specifically for attachment to the sides of ships. Its 10lb of explosive was held in a metal canister mounted centrally on a metal frame. Attached to parallel bars alongside the frame were six ‘horseshoe’ magnets. The mine was designed to clamp itself on to the metal hull of the ship until the time set for it to explode. Its delayed-action fuses were chemically operated, with a striker pin held back by a dissolvable celluloid washer. Once the ampoule of acetone was broken inside the fuse, the washer would gradually dissolve over a prescribed period, eventually releasing the striker pin to detonate the explosive. The time taken for this was not exact and could be anywhere between four and eight hours, depending on the strength of the acetone and the temperature of the water. If several limpets were placed together there was also a danger that the first one to explode would dislodge the others and they would sink to the bottom to explode with no ill effects to the ship. To counter this, a secondary fuse was fitted, which was activated by two processes. First, it had to be armed by dissolving the water-soluble washer that guarded its detonator. This was achieved after an hour in the water. Second, its detonation was triggered in sympathy with the shock wave caused by another mine exploding on the same ship. In theory, one explosion would then set off all the limpet mines attached to the ship, but the fuse was still in its development stage and was not reliable.
To be effective the limpet mines had to be placed well below the waterline on the ship’s sides. To accomplish this task, a placing rod was developed to facilitate the lowering of the mine into the water. The rod was a jointed steel pole 6ft long, capable of being disassembled and stored in the bottom of the canoe. The mine was
hooked on to the end of the rod and lowered into the water before being pushed gently on to the ship’s plates. But this delicate procedure would be complicated by the fact that it would be taking place in the tidal waters of the river and in all possibility with a current of several knots flowing past the canoe. To hold the craft on station during the placing of the mine, the second crewman would fasten on to the side of the ship by means of a magnetic hand-hold to keep the craft still.
To rehearse the placing of the limpet mines, Hasler’s men had the assistance of the Dutch minesweeper Jan Van Gelder. On 4 November they practised attacking her with limpets while the ship steamed at a steady two knots to stimulate a tidal stream. Two days later they were at sea in the newly commissioned submarine P 339, HMS Taurus, trying out the makeshift mechanism and the procedure for launching the cockles at sea. Both of these processes were run through again and again in the subsequent days until the section had fully mastered the techniques required.
A magnetic limpet mine preserved at the Combined Services Military Museum in Maldon, Essex. The thumb screw on the left of the mine unscrewed to allow an acetone ampoule to be inserted. Tightening the screw shattered the ampoule and allowed the acetone to come into contact with the celluloid washer holding back the firing pin. The orange fuses used in Operation Frankton allowed for a nine-hour delay. (Courtesy of Richard Wooldridge, Combined Military Services Museum)
On 9 November the party moved south to Margate in Kent. Hasler had organized a full-scale rehearsal of Operation Frankton to test his team. Operation Blanket had been devised to simulate the journey up the River Gironde to Bordeaux. The men of No. 1 Section were ordered to set off from Margate, paddle their way round to the mouth of the River Thames and then make their way 50 miles upriver to the London Docks unseen and undetected. The district naval commander had been warned of the exercise and the coast defences were all on the lookout for the canoes.