SPY TRAP - The Real Story


I first encountered the amazing story of the Oerlikon gun, whilst undertaking research for a planned novel based on the invasion that never was. This was the so called Operation Tannenbaum -  Germany’s planned invasion of Switzerland. As a resident and now citizen of Switzerland, quite how the Alpine Republic had managed to avoid occupation by the forces of the surrounding Axis powers had intrigued me for some time. However, as soon as I read about the ‘Gun from Switzerland’ I was hooked and determined to base a novel on the heroic events of the late summer of 1940.


Despite the fact that it is a fascinating story, little has actually been published about how Britain actually acquired the capability of producing the Oerlikon gun at home. What follows is a brief outline of what is known about this whole story, I leave it for the reader to judge whether or not I have done it justice. The only ‘real’ person included as a major character in the book should be easily recognisable; for Stephen Milton read Steuart MItchell. Others, such as Louis Mountbatten, Claude Dansey and the Head of Naval Ordnance make only cameo appearances.


In order to appreciate the significance of the Oerlikon weapon, one has to go back to the period after World War One. The attacking potential of aircraft was only just dawning on military leaders when that war ended.However,  by the late 1920s, The British Admiralty was so concerned about the risk to its capital ships of attack from the air, that they had commissioned the development of at least two specialised anti aircraft weapons.


Both of these had noted disadvantages, either being bulky and expensive or firing light, ineffectual bullets. Lord Louis Mountbatten was one of the naval officers most concerned about the dangers from air attack and it was in his capacity as a Commander in the Naval Air Division, that he was first made aware of the Oerlikon 20mm cannon. Not only was this weapon specifically designed to cope with the new threat of dive bombers, it also had a very rapid rate of fire and was comparatively light and easy to move and mount. It was also marketed by an extremely gifted salesman Antoine Gazda.


After arranging for an initial demonstration of the weapon’s capability, Mountbatten faced a wall of indifference from The Admiralty and throughout 1937 and 1938 he fought a pretty much isolated campaign in support of the Oerlikon.


It was only when Sir Roger Backhouse, an ex gunnery officer himself, became C-in-C , Home Fleet, that Mountbatten acquired an ally in high places.When Backhouse became First Sea Lord, the door was open for the Oerlikon and in 1939 an order of 1500 was placed with the Zürich factory.


As an indication of their real interest and concern, Steuart Mitchell, a member of the civilian staff of the Chief Inspector of Naval Ordnance, was sent to Switzerland in April 1939. An ex gunnery officer, invalided out of the Royal Navy, Mitchell’s role was to prove crucial. Initially, however, things did not go to plan; such were the delays and complications that a mere 109 had been delivered by the time that France fell to the Germans’ Blitzkrieg.


Having arranged for his wife and two Naval Attaches to return to Britain before France fell, on June 16th Mitchell himself attempted to escape the almost encircled Switzerland. He took with him  vital technical drawings and three sacks full of jewel centres for aircraft instrumentation. The documents were absolutely crucial, because even though an agreement to franchise production of the guns in Britain had just been reached, the British had no specifications, on which to base their production. Without the drawings, therefore, it is inconceivable that production of the 20mm cannon could have begun in Britain. Moreover, the sacks contained sufficient scarce jewel centres to keep a very embattled RAF going for several months.


As might be expected, Mitchell attempted to reach Spain by car, via Southern France. However, he found his way across the river Rhône blocked by a detachment of Wehrmacht motorcyclists and was unable to proceed. Having returned to Switzerland, he then made his way via the Balkans, to Turkey and then on through Palestine to Egypt, finally flying back to Britain from Cairo. Little detailed information on his route is available and, in developing my plot, I tried to combined what is known of his journey with what was possible and plausible at the time. The fictional Milton’s departure by air  from Locarno to Belgrade was, arguably, possible, although there are different views on these flights. Some sources state that  the special Swissair flights from Locarno to Belgrade took place only in May and June 1940, whereas other sources are less precise over the timings of  these flights. What is certain is that they were used to move gold on behalf of the Schweizerischer Bankkverein and as a route out of Switzerland by British military personnel. I trust that those who believe my use of this escape route for Milton to be anachronistic do not find their enjoyment of the book overly spoiled by my timing one of the last of these flights on August 1st 1940.


The Simplon Orient Express continued to run from Lausanne to Istanbul (via Belgrade) until October 1940. The most plausible way to reach Egypt and Cairo from Istanbul would be via the Taurus Express, which crossed Turkey, Syria, the Lebanon and Palestine. It was the case that, at that time, the Taurus Express ran with a road section between Tripoli and Haifa. There has been some confusion among some readers that Tripoli refers to the capital city of Libya. Of course, the Tripoli which appears in Spy Trap is a city of the coast of The Lebanon.


Yeşilköy was a mılıtary aırport ın 1940 and bızarrely, at that time German engineers were working on its improvement. The German paver, so vital to the plot is, however, entirely my creation.


Domestic production of the 20mm Oerlikon cannon began at Ruislip in late 1940 and the first deliveries were made to the Royal Navy in March 1941.


The RAF Regiment, which was that section of the air force responsible for the defence of airfields from enemy attack, also made great use of this weapon’s anti aircraft capability. The Oerlikon was, in fact, the main armament used by its Light Anti-Aircraft Squadrons operational in North Africa, the Middle East, Italy, North Western Europe and the Far East.


While there are no specific statistics on the number of  guns  built in Britain, it is known that by 1945, some 55000 of them were in active service in the British and Commonwealth navies. Its small size, easy installation and lightweight quality made it ideal to fit as a defence weapon on submarines and smaller ships. Indeed, some Auxiliary vessels of the Royal Navy still carried the Oerlikon in 2006!


Otto von Menges was given the task of producing the first plan for Operation Tannenbaum, the planned Nazi invasion of Switzerland, which, of course, never took place.