ROYAL NAVY HARBOUR DEFENCES - OBAN

Oban is a small town on the western coast of Scotland near the island of Mull about 95 miles North of Glasgow. During WW2, merchant ships gathered there under the protection of the Royal Navy and joined up with larger convoys to the USA, Russia and elsewhere.  A few miles to the north is Ganavan, a headland which offers an excellent view of the waters around Oban.  It was on Ganavan headland that the Royal Navy established the "Little Ganavan" anti-submarine Indicator Loop Station and a Port-war Signal Station (PSS). As well, there was a radar tower, a plotting room, gun emplacements and ammunition stores.  This is the story of the Oban Indicator Loop Station at Little Ganavan.
 
 
If you have any feedback please email me:

Dr Richard Walding  
Research Fellow - School of Science
Griffith University
Brisbane, Australia
 Email: waldingr49@yahoo.com.au
LINKS TO MY RELATED PAGES:

  • Indicator Loops around the World (Home Page)
  • How an indicator loop works
    The photos and measurements were taken by Martin Briscoe of Fort Williams, Inverness-shire, on Sunday 7th May 2000. This page was updated on 3 February 2012.  I'd also like to thank Neil Owen of Oban for additional information and photos. The Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS) has the Oban Indicator Loop Station (at Ganavan) on their Canmore database.


    The map below shows the disused harbour defence control huts used by the Royal Navy for its antisubmarine indicator loop defences in World War 2. They are located at Ganavan headland near Oban Bay - Argyll, Scotland - 95 miles North of Glasgow. The land is currently owned by Dunollie Estates and tenanted by farmer Alaistair MacLeod - a special constable at Oban. Anti-submarine ‘indicator loops’ are long lengths of cable laid on the seabed in shipping channels of strategically important ports. They rely on the production of an induced current in a stationery loop of wire when a magnet (in this case, a submarine or surface ship) moves overhead. Even if wiped or degaussed, ships (including submarines) still have sufficient magnetism to produce a small current in a loop. The current is detected by galvanometers at a Loop Control Station on the shore. This technology was developed by the British Royal Navy at HMS Osprey (Portland Naval Base) and HMS Vernon starting back in 1915 and first deployed at Scapa Flow, in the Orkney Islands at the northern tip of Scotland. In 1996, a portion of the Oban Bay loop cable was brought to the surface by a clam dredger about 500 m offshore from the island of Lismore just to the north of Lismore lighthouse. It was actually marked as a navigation hazard for a time. Encrustation meant that the cable is now a pretty inflexible and bulky object.
     
    Photo of Ganavan headland taken in 1945. During the war the area was surrounded by a barbed-wire fence and the huts were hidden in the bush and not visible from the road or the signal station. Today, the area is grassy and the remains are quite visible.


    A BRIEF HISTORY

    In the 1930s, Admiralty policy was that important harbours should be progressively defended by fixed anti-submarine defences consisting of one or more indicator loops. Loops took a fair while to survey, plan and lay and this lead time was thought necessary. If hostilities arose, the plan was that the Royal Navy would then lay harbour defence Asdics (HDAs) and controlled mines.  However, it became apparent that the cost of repairing and maintaining existing loops was becoming prohibitive so the laying of more loops had to wait until conflict occurred. By 1938, the possibility of conflict with Germany was most likely so loop laying was stepped up. By 24th August 1938, four ports were protected (Portsmouth, Portland, Plymouth and Firth of Forth) with the Straits of Dover being added in Autumn 1939.  Two others - at Penang and Singapore - were also under RN control.  Others, such as Falmouth, Berehaven, Queenstown, St George's Channel, North Channel and Tynemouth were planned for 1940-41 as well as overseas loops at Singapore, Alexandria and Malta.  No loop station was planned for Oban Bay.

    In early 1940, with the imminent fall of France and the threat of invasion, many emergency coast batteries and harbour defence stations were constructed. On the 6th February 1940, the Admiralty decided that Oban Bay should be used as an additional naval base to the Kyle of Lochalsh, which was the gathering point for convoy ships but could not provide the facilities that Oban could. The role of the navy was to protect and administer the harbour and surrounding waters, to accommodate merchant ships in the anchorage and organise the sailing of the convoys to join with larger convoys to the USA, Russia and elsewhere. The naval detachment at Oban grew as France fell and more and more convoys were rerouted from the English Channel and South Ireland to the waters between Northern Island and Scotland. The loss of the Irish ports was greatly felt.

    The USN set up about a dozen 'loop receiving stations' on the East Coast, Panama and San Francisco. The Royal Australian Navy installed indicator loops at a dozen sites around Australia and Port Moresby from 1939 to 1942. Loops were also installed by the RNZN at Auckland Harbour in 1942, and by the RCN at Saint John, Digby and Prince Rupert (Canada) from 1942 onwards.
     

    GERMAN RECONNAISSANCE PHOTO
     

    This Luftwaffe reconnaissance photo of Kerrera Sound was taken in December 1940. It shows the naval base at Oban and aircraft of 210 Squadron RAF at their moorings.

    THE BUILDINGS TODAY



    A panoramic view of the Ganavan headland - looking towards the Isle of Mull. The harbour defence huts are on the right of the photo.

     

    The diagram above left shows the relative location of the concrete huts and slabs.  Only buildings A and E remain standing today. The photo on the right shows the huts as they were in 1945.
     
    Photo 1 - A full view of the headland overlooking Oban Bay. Building "A" - the Loop Control Hut - is on the left and building "E" on the right. The remains of building "F" are in the foreground. The Isle of Mull is in the background to the left and Lismore Island is to the right.

    Photo 4 - Building "E", viewed from the South East.Three rooms: two are 2270 mm x 2070 mm, and the third is 3670 mm x 3670 mm. Photo 5 - Building "E" viewed from the top of the steps that lead East from the Loop Control Hut ("A").

    Photo 13 - The Loop Control Hut ("A") viewed from the West.Two rooms: 2070 mm x 3860 mm; 2480 mm x 3860 mm. Photo 15 - The Loop Control Hut ("A") viewed from the East, seaward side.
     
    Photo 16 - Loop Hut "A" viewed from the seaward side.
    The white building on the hill behind it is the Naval Signal Station.
     
    The floorplan of the Loop Control Hut (Building "A"). Walls are double thickness brick (230 mm wide) and the windows are 1200 mm wide and 900 mm deep. On the right there is a small hole in the wall through which cable (probably power) runs. Above it are four pieces of dowel embedded in the wall to which some equipment was affixed.


     

     
    The rear wall of the right hand side room (the Indicator Loop Room) of the Loop Control Hut as it is today. The rear and right-side windows are now open to the elements. A doorway leading to the left room (Binocular Room) can be made out. This photo of a naval rating in the Indicator Loop room of the Control Hut was taken during WW2. It is the same room as shown directly above. The rear and side observation windows and frames are clearly discernable although the equipment being monitored by the rating is not clear. The wooden door, door jamb and cement-rendered brick is visible.
     
    Photo 20 - Building "E" viewed from the rear. Building "E" - floorplan. The walls are double layer bricks about 230 mm wide. Because this is down in a bit of a hollow and has no view of the loop area, it is suspected that this building may be a generator room or store.

    LOOP CABLE LOCATIONS
     

    There were two loops at Oban Bay. Loop 1 went from Ganavan headland (just a little bit north of Maiden Island) across to the beach to Gorten just north of Loch Dun on the Island of Mull. Loop 2 stretched from Craignure (on Mull) across the Sound of Mull to the tip of the Morven district (Rubha an Ridire).

    LOOP CABLE SAMPLES

    Coming ashore at Gorten on Mull (see map above) are some cables that are most likely WW2 "tail" cables for the No. 1 Indicator Loop. The cables were photographed by Geoff Twibell. He describes them as follows: There are some six steel-sheathed cables in all, three of them having frayed down to the inner cores. One contains four rubber-covered cores - possibly "loop tails". Another contains a single, larger core. The remaining cable is post WW2 and contains four PVC insulated cores one red, one blue and two white.
     

    The six armoured cables at Gorten Gorten shoreline with hut in background. Cables run up this rocky shore.

     
    Probable Indicator Loop "Tail" cables The telegraph hut - post WW2

    R.A.F. BASE AT GANAVAN SANDS

     At Ganavan Sands beach (on the north side of the headland where the loop huts were located) there was an RAF flying-boat base where maintenance and training was carried out. A hanger and several engineering sheds were built there to house the operations.

    Number 302 Ferry Training Unit based at Ganavan Sands Ganavan Sands Caravan Park toda

    The photo above on the left shows the Number 302 Ferry Training Unit based at Ganavan Sands where they trained crews to fly their aircraft over long journeys to such destinations as Africa, Asia and even Australia. The photo on the right is of the Ganavan Sands Caravan Park today. Little remains of the RAF base, however, the steel runners of the hangar doors and the former generator shed still remain. The indicator loop huts were on the headland at the rear of the photo. RAF Base image taken from Paul Burns' RAF Oban web page.

    OBAN - MINEFIELD CONTROL TOWER
     There is a minefield control tower at Gallanach overlooking the Sound of Kerra; it lies on the hillside on the south side of a caravan park.
    For more details, have a look at Nick Catford's photos and text on the Subterranea Britannica web site.

    HELP!

     If you know of other WW2 indicator loop stations around the world, please contact me with some of the details so we can correspond.

    I'm particularly interested in getting information from officers and ratings who worked in the loop stations or laid the loop cables. Also, many scientists were involved in the research at the Royal Navy's "Underwater Detection Establishment". Are you still out there?
     

    "Wren's Eye View"
    - The Adventures of a Visual Signaller by Stephanie Batstone. Published by Parapress Ltd, 5 Bentham Hill House, Stockland Green Road, Tunbridge Wells, Kent. ISBN 1-898594-70-8. The first edition (1994) was revised and launched on 5th May 2001 with an extra chapter added in which she describes the reunion with USN Signalman Jack Campbell she got to know at Oban.

    The following extract talks about the loop station at Oban Bay (Little Ganavan Beach). The author, Stephanie Batstone, was a 21 year old visual signaller working at the Royal Navy signal station to the south. In a letter to me (8th September 2001) she said that she never actually saw the loop huts as they were completely fenced off and quite invisible from the coast road and from the signal station. She said no photos were taken of any of the huts: 'penalty of death I should think'. This extract is used with permission of the author.
     


         Chapter 3 - The Loops


    Next morning Carol and Rosemary reported at 0800 to take over our first watch officially from Fred and Alf. Joan and I relieved them at 1300. We thought what a beautiful romantic walk it was, though the autumn sunshine, better than sitting at a typewriter in London. Past Dunollie Castle on the right we went, along the shore of the little bay with a stupendous view of sea and mountains opening up on our left through a kaleidoscope of shimmering russety leaves, round the headland with its cliff face on the right, over the barbed wire fence, and then a stiff climb up the far side.

    There were blankets hanging oyer the balcony railings. In the bright sunlight they looked very grey. Carol and Rosemary had their sleeves rolled up. 'We've been cleaning,' they said, 'it's filthy. Only one signal. There doesn't seem to be any more coal just the bucket Fred left. Best of luck,' and they were off down the hill. 'There's a hole in the kettle,' Joan said, 'and it's awfully rusty. I wonder if Fred took the good kettle?'

    'What did Dave say about that little phone with the handle on the box?' I said.
    I couldn't understand,' said Joan. I hoped you had. Something to do with loops.' At that minute it rang huskily.

    Joan snatched it up and said in a quavering voice, 'WSS' I could hear a male voice the other end say, 'Little Ganavan - Bert here our DO is on the way up to check your CBs'. The line went dead.

    We looked at each other thoughtfully, registering DO as Duty Officer and CBs as Confidential Books. But where were they, and why did he want to check them, and what had Dave said Little Ganavan was? Anyway, the place looked fairly clean. We rolled our shirtsleeves down and put our jackets on to be on the safe side.

    Ten minutes later a rather elderly Sub-Lieutenant RNVR (thirty at least) with a propitiating expression came panting up the steps. It's OK,' he said, 'they're in that little grey tin box on the wall, and the key is under the telephone. Did Dave tell you I have to come and check them once a week?'

    'No - oh, yes,' Joan said. It was probably politic not to let Dave down. We stood respectfully while he checked the signal and code lists. 'Dave explained about the loops, did he?' he said. 'Oh yes,' I said. 'Good, good,' he said. 'Well, remember we're not far away, if you ever want a hand. ''Thank you,' we chorussed, as he executed a deft descent of the outside ladder, missing several steps (a skill which we made a mental note to acquire as soon as possible). 'Don't forget the Ensign,' he shouted up, 'and the gale cone.'

    At that moment the husky phone rang again. He rapidly reversed his ladder drill, coming up three at a time, and picked up the phone. 'WSS' 'Little Ganavan, sir,' said a male voice. 'Crossing on one.' He shot a practised eye over the expanse of sea. I indicated a telescope but he waved it away and snapped back, 'Fishing boat, Maid of Mull, outward'.

    He flashed us a dazzling smile, said rather apologetically, 'She always goes out about this time,' and was away, galloping down the side of the cliff like an antelope.

    It seemed odd to us that at Cabbala, where it didn't really matter, everyone had gone to such trouble to explain everything. Here, where it patently did matter, nobody thought any explanations necessary. We tried to piece it together.

    'There are two loops,' said Joan, 'one stretching across the Firth of Lorne and one across the Sound of Mull, under the sea.' 'And every time a boat crosses one of them it gives off a bleep. ' 'Where?' In Little Ganavan!' 'But where is Little Ganavan?'

    'Could it be all that barbed wire and notices saying no admittance, RN property, at the bottom of the cliff? That's the only thing that's quite near.' 'You can't see any buildings. They must be right on the beach.' 'Then they sit there watching a radar screen - have you ever seen a radar screen?'

    'Yes - a little round window in the dark - there was one on the battleship we got on in Liverpool docks. It's awfully new - the latest thing. Sort of green and blurry, with a wiggly line going across the middle. When it sees anything, the line jumps up and down.'

    'So when it does that, they phone us up and say "crossing on one" or "crossing on two" and we look at the sea and tell them what ship it is.' 'Supposing we don't know.' 'We flash it up, you clot, and get its name.' 'How do we see it at night?' I suppose it'll have some lights.' 'And supposing we can't see anything?' 'Then we tell them, and it must be a submarine.'

    We looked at each other with widening eyes, visualising a sleek sinister shape gliding into Bonnie Oban Bay to blow it to bits, or to land Conrad Veidt in dark glasses at Dunollie Point to mastermind a plot to assassinate Churchill. It would all be our fault. I looked again at the sea. I don't know how he could see that fishing boat,' I muttered. 'And we've got to know whether it's naval and we give it the code of the day challenge, or international and we give it the unknown ship call.'

    * Note: The green radar screen referred to above was at the Radar Station not inside the Loop Hut.  An indicator loop uses pen and ink to record a line on a continuous roll of paper about 8cm wide. The photo below was taken at the Pennyfuir Gates. The radar towers are visible in the background.