Highball Bombs

 During World War II, Loch Striven, one of the Clyde’s more secluded sea lochs, was used as a training and testing area for special forces. This was due to its remote location, poor access by road and relatively few inhabitants. Two of the now well known groups to train on the loch were X craft midget submarine crews (HMS Varbel) and the team testing the experimental Barnes Wallace ‘Highball bombs’ which were designed for the attack on major capital ships in protected anchorages. The spherical Highball should not to be confused with the cylindrical ‘Upkeep’ bouncing bomb of Dambuster fame, also developed by Barnes Wallace and his team, although they were of similar design and operation.

Without getting too deeply into the tech behind the Highball’s operation, its worth understanding the basics. Delivery was by medium sized bomber aircraft and initial experiments involved the Vickers Wellington until a specialist squadron was formed in 1943 utilising the De Havilland Mosquito, twin engined fighter bombers, which were based at RAF Skitten in north of Scotland. The Highball was spherical in shape, around 35inches in diameter, weighing c.1250 lbs. and could be detonated by a depth charge pistol within its mechanism, the payload was 600 lbs. of torpex and each aircraft could carry two Highballs.

The key challenge for Wallace and his team was to design and test a weapon which could evade the torpedo nets likely to be set from a large battleship at anchor, yet detonate its payload against the more vulnerable and less well armoured under belly of the ships hull. In other words below its armour belting and below water level. 

The solution was ingenious. The Highball bomb could be dropped far enough away from a target to reduce AA damage to the delivery aircraft, the bomb was designed to bounce or skip across the surface of the water, over the defensive nets, strike the hull and sink. To assist with the bombs bounce and also to help it sink close to the hull, the bomb was spun backwards at 700-900 rpm prior to release from the aircraft. This back spin  assisted bomb flight, bounce and accuracy. Once the bomb had hit the side of the target it would naturally sink, here the back spin would again assist as it would force the bomb against the hull as it sank. Detonation was controlled by depth charge pistols preset to suit the target. 

Testing of the Highball bomb in Loch Striven was conducted with dummy bombs of similar size and weight. The targets for the tests were an old WW1 French naval vessel, the Courbet, and laterally a decommissioned British warship, HMS Malaya. These vessel were anchored across the loch and set up for aircraft bombing runs south to north up the loch. The Courbet was anchored in deep water (50-70m) whereas Malaya was moved inshore into shallower water (25-50m). 

The Highball, although trialled at a number of locations around the UK, was never used in anger. 618 Squadron were never given the green light to attempt their one way mission to bomb the Tirpitz in Trondheim Fjord, Norway. The Tirpitz was eventually disabled by the famous raid of X-craft midget submarines later in 1943, and eventually sunk by bombing attacks by Royal Navy and Royal Air Force aircraft in 1944.

After the war all the work in the loch remained ‘top secret’ and as generations passed any memory of the project was lost. This was until Dr Iain Murray from University of Dundee became interested in the development work on Highball through research of a book he was writing about Barnes Wallace. Dr Murray teamed up with the Northern Diving Unit of the Royal Navy and East Cheshire Sub Aqua Club (ECSAC) with the aim of recovering two Highballs for restoration and display in the Brooklands Museum and the De Havilland Aircraft Museum. The project, undertaken in 2017 was successful.  Project reports by ECSAC can be found by following the link at the end of this article on their website. 

So what can the diver expect to see beneath the surface of Loch Striven? Very simply the remains of a very “hush-hush” WW2 project……a bit of history, developed over 80 years ago. For most, this will be a boat dive.  The main objects of interest are the Highballs, it is believed there maybe up to 200 on the seabed. From the sidescan of the site below many of the dots between 30-50 metres are Highballs lying proud of the seabed, some maybe rocks, but there should be a fair chance that you will find at least one or two on a dive. Also on view is a drop charge casing from an X-craft midget submarine.

Finally there is a more recent addition of a large Bruce mooring anchor and chain, each chain link is around 400mm long, probably left from when commercial ships were mothballed in the loch around 2010. The anchor and chain could be used as a baseline for your dive, as it generally runs north to south from the bruce anchor, parallel to the shore and through the main area of interest.

The anchor is the largest target which sits around 2m high, the side charge sits around 1m high so come armed with a gps receiver and fish finder with zoom facility, preferably with downscan or sidescan apps.

Bruce anchor – 55° 56.982’N, 05° 04.307’W

X-craft drop/side charge – 55° 56.972’N, 05° 04.283’W

When we last dived the site in 2022 there was a light red rope strung between the side charge and a group of 3 Highballs lying close to the chain (east side). See sidescan plan above.

The seabed is composed of mud and fine silt so care is required not to disturb, tidal streams will be weak at this area of the loch so it maybe worth diving mid tide to reduce the risk of a ‘fog out’.

The Highballs are perhaps not a site you will visit often but none the less they provide a dive of much interest, and the opportunity to see and film some rare artefacts from WW2.

If you would like further information regarding the project to recover two Highballs by Dr Murray and East Cheshire SAC please follow this link.