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David and Big Bertha, A Short Lived Affair

19th January 2013

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Photograph of David and Big Bertha,  A Short Lived Affair

(by Andrew Guttridge)

This article was first published in the Annual Bulletin of Caithness Field Club 2011.

How the RAF gained and lost a naval big gun.

The fighter airfield at Castletown was placed on the edge of the Pentland Firth primarily as part of the Orkney defences to protect Scapa Flow but also providing aerial protection for Naval and Merchant vessels travelling around the north of Britain. The station opened on 28th May 1940 and its first commanding officer, Wing Commander David Frances William Atcherley, arrived on 8th June to assume command of the station.

David Atcherley and his twin brother Richard were at the time two of the most well known, some would say notorious, pair of figures within the service. Born in 1904, both brothers had developed an intense love in flying from a very early age and had joined the RAF at the earliest opportunity, neither ever married but devoted their entire lives to the service. In the 1930s anyone with an interest in flying would have known the name Atcherley as Richard had made a significant mark for himself both in and out of the service as a skilful exhibition pilot spending many summers participating in flying circuses in Britain and the USA, he was also one of the RAFs winning Schneider Trophy team in 1929. David, although an equally skilful and accomplished pilot, preferred to avoid the limelight and mainly kept his flying activities out of the public eye.

As RAF officers they were vey popular with officers and men alike and well respected by all who served with them. They were highly individual even eccentric characters, their idiosyncratic approach and personal disregard for formal procedure and protocol when it got in the way of getting the job done, often exasperating their superiors. However the job always got done and usually with a speed and efficiency that ensured their advancement. It is undoubtedly these traits that are responsible for RAF Castletown having its own big gun.

David was at this time 36 years old and had over 13 years service in the air force. As the commanding officer of No. 253 squadron he had recently spent some weeks involved in the fierce air fighting over northern France in the lead up to the evacuation from Dunkirk. Before the evacuation itself however he found himself posted to the far north of Scotland to command the new fighter station of RAF Castletown.

This was Davids first station command and when he arrived the airfield was still very much a construction site with only a few rudimentary facilities. With the typical Atcherley zeal and enthusiasm he immediately threw himself into the task of transforming this collection of huts and asphalt into a functioning aerodrome.

One of Davids main concerns was defence. This was June 1940, the Dunkirk evacuation was only a few days old and France, Denmark and Norway were now occupied. Britain was effectively surrounded and the nation waited nervously for the arrival of the enemy on its shores, shores that were rapidly being fortified with concrete obstacles, pillboxes, minefields and other defences. These defences were all well and good but what was lacking were the weapons to man them, most of the armys tanks, artillery, mortars, guns and vehicles had been left behind on the French beaches and what was left was stretched exceedingly thin on the ground.

The fledgling station at Castletown also had an added problem. The northern boundary of the airfield backed immediately onto the 3 mile stretch of Dunnet beach which was itself considered a potential invasion area. Although invasion obstacles and defences were being erected along the length of the beach it appears that there were initially no troops to provide active defence in the event of an attack.

At this time defence of RAF stations was the responsibility of the army and accordingly a company of Seaforth Highlanders had been at Castletown for ground defence duties since it opened. Station defence remained at this strength for the next few months but it was not until 10th September that additional troops arrived specifically to defend the beach. This was No. 15 Platoon (approx 36 men) from "D" Company 8th Battalion Gordon Highlanders who moved into the Old Mill at Sand End for the purpose of covering Dunnet Bay against a possible enemy landing. To achieve this they were equipped with three Vickers machine guns ! ! !

On the same day the station defence company was replaced by a company of the Queens Own Cameron Highlanders with a strength of 111 officers and men. Although the station record comments this is one of the best armed detachments at Castletown to date, their armament was somewhat below the level for a company at this period and reflects the problem of shortages of weapons.

The defensive position then at mid September 1940 for the defence of the 5 mile perimeter of the airfield and 3 miles of Dunnet Bay comprised some 148 men armed with 3 Vickers machine guns, 9 Bren machine guns, 3 mortars, 2 anti-tank rifles, 133 rifles several pistols and some grenades. Thus these troops were poised to fend off a full scale assault by hundreds of highly trained, battle seasoned troops equipped with tanks, artillery, landing craft and a multitude of powerful weapons. Little wonder Atcherley was desperate to bolster his defences with whatever he could lay his hands on and willing to seize any opportunity that came his way to supplement this meagre stock of weapons.

So when it came to Davids attention some time during June or July that there was a wrecked oil tanker somewhere in his vicinity he immediately flew out to see for himself. His aerial reconnaissance showed that there was still at least one large calibre gun surviving on the wreck and that it may be salvageable. He straight away set about liberating the weapon for his station, an enterprise that was totally unofficial and done completely on Davids own responsibility and entirely in keeping with the Atcherley way of getting things done.

At this time the only occupants of RAF Castletown were 504 County of Nottingham Squadron who had moved over from RAF Wick on the 21st of June. Due to there being no servicing or repair facilities at Castletown as yet, the squadrons maintenance section remained behind at Wick. With no station personnel with mechanical training the only available personnel were the maintenance section of 504 squadron but it required all Davids powers of persuasion, for which the Atcherleys were known, to persuade the squadrons commanding officer, Squadron Leader John Sample DFC, to use his men for such an unofficial purpose.

Salvaging large heavy guns from wrecked ships is not the sort of work that air force mechanics are trained for however they set about the task and to their immense credit, after much difficult and dangerous work, managed to recover two weapons, a 4.7 deck gun and a smaller calibre 12 pounder along with some ammunition, from the wreck.

A concrete hold-fast for the 4.7 gun was built near the station HQ, Castlehill House, at the corner of the plantation opposite the old mill, overlooking what is now a public car parking area. Apparently when the gun was recovered the mounting mechanism that allowed it to traverse was left behind on the ship so the gun had to be installed in a fixed position, the direction chosen left it pointing in the general direction of Dunnet Head lighthouse much to the consternation of the lighthouse keepers. Almost inevitably the gun was given the nick-name Big Bertha. The 12 pounder was mounted on a lorry and, along with two other lorries mounting 2 and 4 Browning guns respectively, made up a mobile anti-aircraft defence for the airfield.

A gun team was hastily concocted from ex-naval and army gunners scrounged from 148 Coy. A.M.P.C.i, who had recently arrived on the station to carry out general construction work around the airfield and who were most probably responsible for building the guns hold fast. Bertha was emplaced and ready for action by 1st September but she was prevented from firing during the full scale Station Defence exercise held on that day because, according to 504 Squadron, the Navy had a word to say about it. I take this to mean that the navy were not at all happy, at least on this occasion, with the possibility of some ill trained trigger happy airmen lobbing 4.7 shells over the top of Dunnet Head towards their ships in the Pentland Firth. The Navy were quite well aware of how easy this was as they themselves were quite fond of doing just this during practice shoots in the Firth, their shells landing in Dunnet Bay and around Murkle.

See Photo Gallery link near the top of this page for a map and gun position illustration.
Map Of Dunnet Head and Castletown showing line of fire.

The Navys unease seems to have been allayed, probably by Atcherleys persuasiveness, because three weeks later on the 20th a practice shoot of three rounds was fired at a target on cliffs to the north side of Dunnet Bay. The first round fell some 400 yds short, landing in the water. The second, a high explosive round, burst at the foot of the cliff. The sights were raised by 300 yards and the third shot hit near the top of the cliff. This was seen as an entirely satisfactory exercise and it was now considered that an attempted landing on Dunnet beach should prove very unhealthy to the would be invader.

Thus Big Bertha left the Merchant Navy and joined the Royal Air Force. David seems to have been quite proud of his big gun and took every opportunity to show off his stolen weapon, he even had the audacity to show it off in front of Royalty and senior naval officers. On the 13th October Major General H.R.H. the Duke of Gloucester, accompanied by Brigadier D. Wimberley, M.C. and some of his staff paid a passing visit to RAF Castletown. Atcherley arranged to meet the Dukes party at the gun position and proceeded to show it off to his Highness. The Duke obligingly inspected the gun and its crew then chatted with David for a few minutes before leaving for Thurso.

David, obviously wanting the gun to be an entirely RAF show, had members of the station personnel trained in gun drill by the Pioneer Corps crew. The RAF crew had their first shoot on the 6th of November at around midday when David took another opportunity to show off Big Berth to a distinguished gathering of Naval, Army and Air force officers who witnessed the RAF guns team fire the gun for the first time. Two rounds were fired at the target on Dunnet Head with accurate results.

The last recorded firing of the gun was on 23rd December 1940 at 3:15pm when two practice rounds were fired at the target on Dunnet Head.

Davids affair with Big Bertha finally came to an end when he overplayed his hand with the Admiralty. According to John Pudney in his biography of the Atcherley twins, having used up all the ammunition salvaged from the tanker, he tried to indent the Admiralty for 130 rounds of ammunition from the Royal Navy depot at Chatham. The navy immediately smelled a rat and demanded to know why an RAF station was drawing ammunition for a naval gun.

The game was up and very shortly a party of indignant naval gunners appeared at Castletown to reclaim their weapon, and so after only a few months service with the RAF Big Bertha was dismounted and transported away to re-join the navy. Shortly after her departure David himself left when, on 14th February 1941, he was posted away to command No. 25 night fightr squadron where his unorthodox approach did much to develop the use of radar assisted night interception techniques.

Bertha did however leave a trace of her brief service with the RAF. A 14m gap in the drystone wall running beside the road to Castlehill harbour behind which the concrete holdfast with a 36 diameter ring of twenty four 1 bolts set into it still exists, now completely overgrown. At the foot of a small tree near the rear edge of the concrete apron surrounding the holdfast, the letters RAF are picked out in beach pebbles. As the concrete apron surrounds this tree it must have been left in situ as camouflage, nearby is a tree stump cut off at about 3ft, presumably to prevent it obstructing the guns barrel.

From the records we know that practice shots were fired at cliffs on north side of DUNNET BAY. From an examination of the gun position the only cliffs of any substantial height visible within the field of fire are those of Dwarwick Head, below the Northern Gate House. If the gun was indeed pointed at Dwarwick Head, and considering that this type of gun had a range of over 9 miles, Dunnet Head lighthouse lies only 5.4 miles away almost directly in the line of fire!
Whether Davids gun would have been effective had it been required to defend Dunnet beach from invading craft is doubtful. The gun was positioned to fire across the bay, on the fixed mount any target such as a landing craft heading towards the beach would only be within shot for a very short time as it passed by. The gunners would not have been able to range their shots so the chances of actually hitting anything would have been more luck than skill. It would seem that Bertha was more effective as a moral booster than a real deterrent.

Who Was Big Bertha?
The records tell us that Big Bertha was a Naval, now R.A.F. 4.7" gun and that it was obtained from a sunken oil tanker, so it was a naval 4.7 deck gun mounted on a merchant ship.

The 4.7 calibre came into service in 1888, it was widely used on naval vessels and was the main armament on destroyers. There were 5 versions, or marks, of the 4.7, Mk I to Mk V. Mks I to IV were already obsolete for warship use before the start of WW1 but many were re-mounted on merchant ships and troopships. It is unlikely that any surviving guns would have been re-used in WW2, even on merchant ships.

The Mk V was not adopted by the Royal Navy but during WW1 Britain acquired 620 of a Japanese manufactured version of this gun and mounted them on merchant ships and troop ships with the designation Mk V*. Many of these guns were again used in WW2 to arm merchant ships and troop shipsiii. The final version of this calibre gun was a Breach Loading version from 1918 and was still in service at the start of WW2. It is therefore unlikely that this version of the gun would have been used on merchant vessels, the navy keeping them for its own ships.

From this information we can speculate that Big Bertha was most likely one of the Japanese manufactured Quick Fire Mk V* guns. It had a maximumrange of 16,500yards (15,100 m) or 9.375 miles (15 Km).

Where Did Big Bertha Come From?

During the period from the outbreak of the war to the approximate date of the salvage (September 1939 to September 1940) there were only three oil carrying vessels recorded as sunk in the seas between Rattray Head and Cape Wrath; Shelbrit I, Gretafield and San Tiburcio. Shelbrit I and San Tiburcio sank in deep water miles off the coast so it cannot be either of these, it is therefore almost certain that the vessel from which Big Bertha was salvaged was the S.S. Gretafield, a 10,000 ton oil tanker that had foundered in Dunbeath Bay on 15th February 1940. The Gretafield had been torpedoed by the German submarine U-57 in the early hours of the 14th about 12 miles east of Wick, two massive explosions ripping open her tanks and spilling their burning contents of fuel oil over the ship and the surrounding sea.

The blazing ship did not sink though but was carried by the tide and eventually drifted ashore on the south side of Dunbeath Bay where she remained burning for several days. On the 19th she broke in two and was declared a total loss. The wreck at the time was lying on its keel with its superstructure above water and would have been fairly easily accessible from shore.


Baird, RN, Shipwrecks of the North of Scotland, (Birlinn Ltd., Edinburgh, 2003)
Pudney, John, A Pride of Unicorns, Richard and David Atcherley of the R.A.F. (Oldbourne Book Co. Ltd., 1960)
Quarrie, Bruce, Action Stations 10: Supplement and Index, (Patrick Stephens Ltd., Cambridge, 1987)
Smith, David J, Action Stations 7: Military Airfields of Scotland the North-East and Northern Ireland (Patrick Stephens Ltd., Cambridge, 1984)
Operations Record Book, R.A.F. Station Castletown, The National Archives, Kew
Operations Record Book, 504 Squadron R.A.F., The National Archives, Kew


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