BBC2 recently broadcast a documentary titled The Fall of Singapore – The Great Betrayal. The synopsis from the BBC’s website says that:
Pearl Harbor and the Fall of Singapore: 70 years ago these huge military disasters shook both Britain and America, but they conceal a secret so shocking it has remained hidden ever since. This landmark film by Paul Elston tells the incredible story of how it was the British who gave the Japanese the knowhow to take out Pearl Harbor and capture Singapore. For 19 years before the fall of Singapore to the Japanese, British officers were spying for Japan. Worse still, the Japanese had infiltrated the very heart of the British establishment – through a mole who was a peer of the realm known to Churchill himself.
The main contributors to the programme were Prof. Richard Aldrich of Warwick University, a leading historian of the British intelligence services, and Dr Antony Best of the LSE, an expert on Anglo-Japanese relations. Many of the assertions made were justified by reference to primary documents in the UK National Archives.
At the end of the First World War, the Royal Navy led the world in naval aviation. Japan, which was then allied to Britain, attempted to obtain details of Britain’s new aircraft carriers. Ten requests for information were rejected, but Japan was allowed to recruit a civilian mission.
It was composed of former members of the Royal Naval Air Service, which had merged with the Royal Flying Corps to form the Royal Air Force in April 1918. The mission was led by an experienced naval aviator, William Forbes-Sempill, the Master of Sempill and the son of a Scottish peer. It was in Japan during 1921-23.
The programme argued that the British mission allowed Japan to develop the naval aviation that enabled it to attack Pearl Harbor and to sink Force Z, composed of HMS Prince of Wales and Repulse, off Malaya in December 1941. This is perhaps going too far; Stephen Roskill contended in his history of the RN between the wars that the Japanese would have caught up with the RN and USN eventually, but that the Sempill mission speeded up the process.
The programme suggested that the Japanese needed British help in order to develop naval aviation. They were behind Britain and the USA, but not by as much as the programme suggested. The first deck landing on an aircraft carrier was on HMS Furious on 3 August 1917, which then had a short flight deck forward of her superstructure.
The first carrier with a full length deck was HMS Argus, which was converted from an incomplete liner and completed in September 1918. Britain began construction of the HMS Hermes, the world’s first purpose built carrier, on 15 January 1918. She was launched on 11 September 1919 but not completed until February 1924.
Japan, meanwhile, laid down its first carrier, IMS Hosho, on 16 December 1919. She was launched on 13 November 1921 and completed on 27 December 1922. The first take off from and landing on her deck took place on 22 February 1923. The first landing on a carrier that was underway was on the USS Langley in November 1922. Conversion of the Langley, the USN’s first carrier, from a collier had been completed on 20 March 1922.
The claim made by the programme that the Japanese needed British help to build a carrier would seem to be an exaggeration, since the Hosho was under construction before the Sempill Mission arrived in Japan, but the mission clearly helped the Japanese to develop carrier aviation quicker than they could have managed if starting from scratch.
The second in command of the base from which the mission operated was Yamamoto Isoruku, in 1941 commander of the Japanese Combined Fleet and mastermind of the attack on Pearl Harbor. By 1941 the IJN was well ahead of the RN and at least equal to the USN in carrier aviation, so the Japanese had taken the initial lessons taught to them by the Sempill Mission and built on them by their own efforts. One of Britain’s problems was that most of its naval aviators transferred to the RAF in 1918, so it had few senior officers with air experience in 1939.
Another former RNAS pilot, Frederick Rutland, was recruited by the Mitsubishi company and taught the Japanese deck landing techniques. He was the son of a labourer and was promoted from the ranks. He was known as Rutland of Jutland because he carried out a reconnaissance mission at the Battle of Jutland.
MI5 became suspicious of Sempill’s links with Japan and tapped his phone and intercepted his mail. This provided evidence that he was supplying Japan with secret information. Britain had broken some Japanese codes and intercepted Japanese diplomatic cables relaying some of these from London to Tokyo.
A meeting chaired by Sir Austen Chamberlain, the Foreign Secretary, decided not to prosecute Sempill. His position in society would make this embarrassing, but there was also the perennial problem with espionage cases that it would be hard to convict without revealing secrets, including the fact that Britain had broken Japanese codes. The relevant files are now publicly available in the National Archives, but were kept secret for many years.
There are no MI5 files on Sempill from the 1930s in the National Archives. One from the 1940s states that he was a paid consultant for Mitsubishi in 1931. He needed the money as he was overdrawn by £13,000; nearly £750,00o in 2012 terms.
Whether or not Sempill was involved, Japanese espionage against Britain continued during the 1930s. In 1931, Japan invaded Manchuria. This raised fears of an Angl0-Japanese war, and Britain re-started work on a large naval base at Singapore. The programme suggested that construction began in 1931; in fact, building started in 1923 but was suspended more than once during the 1920s due to changes in government and budgetary constraints.
During the 1930s Japanese businessmen bought up large amounts of property in Malaya. The programme argued that many of them were spies. Japan bought the plans for the Singapore base from a British serviceman called Roberts.
The Singapore base was heavily defended against attack from the sea. The British thought that it would be impossible to invade Malaya and then attack Singapore by land. In 1937 Joe Vinden (spelling?), a British Army intelligence officer, reconnoitred the Malayan coast and concluded that an invasion of Malaya followed by a land attack on Singapore was feasible.
Vinden correctly forecast that the Japanese would land at Kota Bharu in north-east Malaya during the November-February monsoon season; others thought that an amphibious landing at that time of year was impossible. His recommendation that funds allocated to coastal artillery be instead spent on aircraft was ignored.
Japan also had spies in Hawaii, one of whom was Rutland. He later told interrogators that he was ordered to report on the attitude of the population to the possibility of war and on the dispositions of the US fleet. The FBI soon became suspicious of his activities.
Sempill was brought back to the Admiralty when Winston Churchill was appointed First Lord of the Admiralty, the cabinet minister responsible for the navy, on the outbreak of war in 1939. Sempill gave an assurance that he would not discuss service matters with the Japanese. However, in August 1941 he intervened to secure the release of Satoru Makahara, manager of Mitsubishi’s London office, who had been arrested on suspicion of espionage.
At the same time Churchill and US President Roosevelt held secret talks at Placentia Bay. Shortly afterwards the British code breakers at Bletchley Park intercepted and decoded a signal from the Japanese Embassy in London to Tokyo that gave precise details of the talks. A report that was sent to Churchill about the intercept remained secret for 60 years; he noted that the Japanese version was ‘pretty accurate stuff.’ It had to have come from somebody close to him.
Richard Aldrich said that the most important Japanese source with access to Churchill was Sempill. A few days later MI5 told Churchill that the Japanese had information about his inner circle. He demanded proof and a month long surveillance operation produced the names of Sempill and Commander McGrath, who had been with Sempill in Japan.
Churchill stated that Sempill could not remain at the Admiralty. When Sempill was asked to resign his commission, however, Churchill said that he only wanted Sempill to leave his current job, not the RN. Antony Best pointed Sempill was a Conservative peer who would have had friends in the Conservative Party. Richard Aldrich argued that interning Sempill would look very bad for the government, which had employed him even though he had been under MI5 surveillance since 1925.
Rutland was deported to Britain by the Americans and interned. He was released near the end of the war and later committed suicide. Sempill was given a choice of either resigning his commission or taking up a post in northern Scotland; the programme did not make it clear that which he chose. He died in 1965.
It was argued that Sempill was not charged under the Official Secrets Act or interned under Defence Regulation 18B because he was a well connected aristocrat and his arrest would embarrass the government. Other members of the upper classes were interned, including Sir Oswald Moseley, founder of the British Union of Fascists and his wife Diana, one of the Mitford sisters, Admiral Sir Barry Domvile and Archibald Maule Ramsay, the Conservative MP who founded The Right Club.
However, none of them had held any government position during the war, whilst Sempill was close to the Prime Minister. This would suggest that embarrassment to the government in general and Churchill in particular for appointing a man previously suspected of supplying secrets to Japan to a sensitive post was a stronger reason for not taking action against him than his social position.
Another reason might be that a trial could have revealed that the British had broken Japanese codes. The programme mentioned this when discussing why he was not charged in 1925, but did not repeat the point when discussing his lack of punishment in 1941.
This was a very interesting programme. It should be noted that it was not as new a revelation as the BBC claimed. The relevant documents were released to public view at the National Archives in 1998, and The Independent newspaper reported on them, quoting Richard Aldrich. Nevertheless, the programme was well made, justified its claims with reference to primary documents and brought the story to a wider audience.
 Stephen Roskill, Naval Policy Between the Wars, vol. i (London: Collin, 1968), p. 529.