Formerly Major Hasler’s Party, RM Beach Patrol Detachment; also Cockleshell Heroes

Date Founded: August 1942

Mission When Founded: Ship attack by MTM, kayak or diver; harbour sabotage by kayak or diver

Mission During the War: Unchanged

Theatre(s) of Operation: Mediterranean, SE Asia

Headquarters: Southsea, Hampshire, UK

# of Personnel: August 1942: 5 all ranks; Autumn 1942: 24 all ranks;

June 1944: 73 all ranks


In the autumn of 1940 keen yachtsman and decorated hero of Narvik, Major H. G. ‘Blondie’ Hasler RM, proposed the formation of a small-boat attack force manned by divers to Combined Operations HQ but the proposal had been turned down as impractical. However, after HMS Queen Elizabeth and HMS Valiant were badly damaged by human torpedoes in Alexandria harbour, and HMS York was sunk off Crete in March 1941 by Italian Motoscafi da Turismo Modificati (MTM) or modified explosive motorboats, COHQ revived its interest, and Hasler was appointed to the Combined Operations Development Centre at Southsea to oversee the unit’s development.

Ostensibly Major Hasler’s Party was to develop British MTM techniques under the cover name of ‘Boom Patrol Boat’, but Hasler created a second kayak section to implement his original proposal to COHQ. The cover name of “Boom Patrol Detachment” covered the unit’s training activity in kayaks and diving along Portsmouth harbour’s boom. Unit members were also trained in underwater attack using the Davis Escape Apparatus. This was a closed-circuit breathing system that left no tell-tale trail of bubbles on the surface. However, it was bulky, liable to get caught, and if it leaked the soda lime used to scrub carbon dioxide from the system would turn into deadly quicklime. Carbon dioxide poisoning leading to disorientation and death was also a distinct possibility.

Using his pre-war small boat experience, Hasler also redesigned the existing folbots so that they had timbered decks and keels, were collapsible for submarine storage and could be launched from a submarine fully loaded and crewed in rough water. These became “Cockle Mk. II”. The submarine’s gun utilised a block and tackle to raise and lower the fully-loaded cockles into the sea.

In December 1942 came the operation that made the RMBPD famous as the “Cockleshell Heroes”. Operation FRANKTON was a raid to attack German blockade runners waiting at Bordeaux-Bassens docks to take special electronic equipment to Japan. The RMBPD were after less than three month’s existence, and the kayak section had another two months to train but the secrecy was such that the raiders didn’t know their target until two days beforehand. Five kayaks were launched by submarine off the French coast, one having been damaged, and paddled 112km up the Gironde River to the target. Four ships were badly damaged but weren’t loaded at the time of the attack. However, eight canoeists either drowned or were captured and executed under Hitler’s ‘Commando Order’. Only Hasler and another marine escaped and returned to Britain in April 1943.

Before Operation FRANKTON, Hasler instructed his 2ic Captain Jock Stewart to develop swimming attacks. Stewart started development work on a lightweight waterproof suit for attack divers with Mr. Goram, Dunlop’s top technologist. Lieutenant Bruce Wright RCNVR (who was attached to the unit whilst preparing his own unit, the Sea Reconnaissance Unit), suggested American-style swimming fins. Goram reinterpreted these and included them on the suit, and moved the breathing equipment onto the diver’s back – the frogman was born. Goram’s other developments include an air-dropped inflatable raft to allow swimmers to attack remotely moored targets. RMBPD personnel helped develop the Motorised Submersible Canoes (MSC) or “Sleeping Beauties”, which were delivered in July 1943.

In 1943 Lieutenant Pritchard-Gordon and the men of Earthworm section were sent to the Middle East to engage enemy shipping in the Mediterranean and the Aegean to clear the way for raids by Raiding Forces Middle East, including the SAS, SBS and LRDG. In June 1944, the RMBPD’s most successful raid badly damaged two destroyers and two other vessels in Laki harbour, Leros. These were finally sunk by the RAF as they were being towed to Piraeus for repairs. The removal of the destroyers allowed raiders to move freely and in greater numbers, and enabled the highly successful Simi raid by the SBS and Greek Sacred Squadron.

In 1944 the RMBPD was organised into a HQ and administration group of 34 men all ranks. This group also carried out the unit’s experimental work. There were three operational groups: ‘A’ consisting of 16 all ranks, ‘B’ consisting of 6 all ranks and ‘C’ consisting of 17 all ranks.

The diminishing returns of attacks led to Earthworm section returning to the UK in October 1944. In June 1944 RMBPD’s CO Hasler was posted to the nascent Small Operations Group (see future DG-WW2 post) as Lieutenant-Colonel and 2ic of the new unit. The RMBPD continued in its training and experimental functions but plans to send sections to the Far East never happened.

The RMBPD was the only British Special Forces unit to survive the end of World War II intact, and one of three Special Service units to survive

(the other two being the RM Commandos and the Parachute Regiment). At the end of the war it was decided that future amphibious operations should be the purview of the Royal Marines, so when the SBS, COPPs, SRU, Detachment 385 returned home from the Far East they transferred to the Royal Marines under the commander of Blondie Hasler.

In 1946, the RMBPD became the School of Combined Operations, Beach and Boat Section at Fremington, Devon. SCOBB quickly became the Combined Operations Beach and Boat Section. In 1948 COBB became the Small Raid Wing of the RM Amphibious School. In 1950 the SRW became the Special Boat Wing organised into “Special Boat Sections”. The present day Special Boat Service directly traces its descent from the Royal Marine Boom Patrol Detachment.


Ladd, James – 1978. Commandos and Rangers of World War II. St. Martin’s Press.

Ladd, James & Melton, Keith – 1988. Clandestine Warfare. Blandford Press

Messenger, Charles – 1985. The Commandos 1940-1946. William Kimber.

Parker, John – 2000. Commandos. Headline Book Publishing.

Thompson, Julian – 1998. The Imperial War Book of War behind Enemy Lines. Sidgwick & Jackson.

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