British Aviation Pioneer Spied For Japan

The 19th Lord Sempill of Great Britain and spy for the Japanese.

The 19th Lord Sempill of Great Britain and spy for the Japanese.

Aside from motive and sex, this British spy story has everything you would expect: money, politics… hmm, I also expect car chases and shoot-outs, but no such luck.

This is the story of Master William Francis Forbes-Sempill (later named the 19th Lord Sempill after his father’s passing in 1934), who sold British aviation secrets to the Japanese in the 1920s, and despite it being known by the highest reaches of British government, news of his duplicity was only revealed in 2002, some 37 years after his death.

Born on September 24, 1893, Sempill came from a privileged British family. That’s him in the photo above.

He joined the Royal Flying Corps as a second looie on August 15, 1914 and became involved in flying duties. By February of 1915, he became involved in the Central Flying School which was where the top flight trainers went to learn how to train on behalf of the Royal Flying Corps.—and was a promoted to full-blown lieutenant by April.

By August – he had started instructing, but by the end of the year he gave up his Army commission after receiving acceptance in the Royal Naval Air Service.

By the end of 1916, aged 24, he had been promoted to squadron commander.

By April 1, 1918 when the Royal Flying Corps. and Royal Naval Air Service combined into the Royal Air Force (RAF), Sempill was appointed one of the deputy directors of the personnel department of the RAF, and received the temporary rank of colonel.

When WWI ended in 1919, he retired from the military and became a test pilot.

When you look at the body of work, Sempill may have received a leg-up from daddy and daddy’s connections, but he continued to rise in rank – and quickly, when only good work would have allowed for that (or greased palms – but no one has suggested that is the case here). Sempill seemed to be a well-liked man who did his duty for King and country.

In fact, while his family came from a long line of military men, his father, the 18th Lord Sempill, was an aide to King George V (reign: 1910-1936).

So what the fug happened? He met the Japanese… and he liked them.

What most people seem to have forgotten, is that Japan and Great Britain—two island nations—were allies during WWI. And so, when Japan noted that it liked the new-fangled aircraft carriers the Brits had, there was no issue in showing them how it was done.


The Brits did not want the Japanese nosing around their new technology, and officially rebuffed them 10 times when it came to inspecting an aircraft carrier. This was war-winning technology, and it was not to be shared.

But the British Air Ministry and Foreign Office had other plans, and felt this was a sure-fire way to make a few quid (slang for Brit money).

In 1920, Sempill led an official non-military British mission to Japan to help organize the Imperial Japanese Naval Air Service and to help them build aircraft carriers and to buy British-made military hardware.

Hunh… now, while I understand allies sharing and all that, the problem was the Brits never thought the Japanese would ever be an equal in war… never be a big-time player… and so the Brits under-estimated the Japanese.

They were trained in aviation and level-flight bombing and torpedoes. But they wanted more, with the crucial bit of technology being the deck, the Japanese were afraid to try and construct one without British aid… which was only too helpful in aiding the construction of the first Japanese aircraft carrier – the Hosho.

Within two years, the British had given the Japanese the potential to have a world-wide reach.

The work done, Sempill and the team left, leaving the facility in the charge of Yamamoto Isoroku (surname first).

Yamamoto was the mastermind behind the Japanese attack on U.S. Pearl Harbor military base, in Hawaii on December 7, 1941. But, as sure as the Rising Sun never sets on the British Empire, Japan certainly wouldn’t have formed such a formidable force were it not for aid received from Great Britain 20 years earlier.

Captain Sempill showing a Gloster Sparrowhawk to Admiral Tōgō Heihachiro, 1921. Source: Tōgō Shrine and Tōgō Association.

Even back in 1922, the U.S. of A didn’t like the growing naval strengths of Japan and wanted to impose restrictions on new Japanese warship building somehow – well, actually it meant that the U.S. wanted Great Britain to abandon its Japanese ally – recalling that the U.S. and Brits are better friends now that no one drinks tea in America.

So The Brits agreed to stop helping Japan… but Sempill, now a confirmed Japanophile, wasn’t able to get the Japanese out of his head.

Now, perhaps it was initially just a job, but Sempill did get along very well with the Japanese, and they with him. In fact, Sempill made close friendships with members of the Japanese military – and maintained them long after Great Britain’s work in helping the Japanese build an aircraft carrier had ended.

Sempill kept in contact with the Japanese Foreign Ministry through the Japanese Embassy in London.

The Japanese military liked Sempill so much they gave him a few awards… like the 3rd Order of the Rising Sun (for distinguished achievements in international relations, promotion of Japanese culture, advancements in their field, development in social/occupational welfare or preservation of the environment); 2nd Order of the Sacred Treasure (for distinguished achievements in research fields, business industries, healthcare, social work, state/local government fields or the improvement of life for handicapped/impaired persons) and some other medal no one is sure actually exists (called the Merit Badge of the Imperial Aero Society of Japan)…

Did the Japanese really like him? Did they like him for his dedication to cause?

Certainly not long after going to Japan for the first time in 1920, he began selling British aviation secrets to the Japanese naval attache, Captain Toyoda Teijiro (surname first) – secrets involving… well… no one is exactly sure, or if they knew, no one really talked about it.

His spying, however, did eventually come to light, but not much was done about it.

In 1925 Sempill led a mission of foreign air officials to the Blackburn Aerocraft Company factory at Brough, in East Yorkshire, London, using his position and name to get into the hangar to take a look at a secret seaplane, codenamed Iris.

Only five of the Blackburn Iris three-engined biplane flying boat were ever built.

Sources indicate that the Japanese had previously asked questions about British aircraft being developed, and at the factory, Sempill asked the same questions, in his official position, of the Iris.

Because of Sempill’s friendship with the Japanese, it had aroused the suspicions of Military Intelligence, who kept a keen eye on his relationship with the Japanese intelligence officer/Naval attaché Captain Toyoda which was cultivated at Japan’s embassy in London. The British Military Intelligence had been keeping Sempill under surveillance since 1922!

And so British Military Intelligence learned that Sempill had been passing secret and classified data to the Japanese. In fact, Captain Toyoda confirmed as much that the data had been paid for – this was discovered… well… read on…

MI5 tapped Sempill’s phone and were keen to observe that he had a servant with a Japanese naval rating.

So… the Brits knew for years that Sempill was a spy, but did nothing about it… until March of 1926, when an oblivious Aviation Ministry proposed that Sempill be named an aeronautical adviser to Greece.

It was only now that the Military Intelligence told the Foreign Office and the British Embassy in Athens, Greece that it could not endorse Sempill to the Greek position because of his possible spying activities with the Japanese.

So Sempill was called in to the Foreign Office for an interview. They confronted him by asking about his loyalty to Great Britain, his friendship to the Japanese and just what had he actually passed on to the Japanese.

But the biggest problem for the Foreign Office was that in order to fully prosecute Sempill, they would have had to admit that publicly that MI5 was intercepting domestic mail to and from the Japanese embassy, and that they had broken Japanese codes. Instead, the Foreign Office tried a different tactic and accused him of openly discussing the secret Iris seaplane with foreign dignitaries and got him to admit he had broken the Official Secrets Act.

Then there was also the scandal involved with the family being close with the British Royals, and being part of the British Establishment.

So… they did nothing, merely denying him his position with the Greeks.

But it didn’t seem to hamper Sempill too much. Although he was then the chairman of the Royal Aeronautical Society – he later went on to become its president. As well, he was allowed to join the Royal Naval Air Service in 1939.

It sure doesn’t sound like he was punished!

As for the Foreign Office, it was red-faced to learn that Sempill and his networking with the Japanese was known by MI5 for at least two years – and even longer if they had chatted with Military Intelligence.

Sempill, however, had balls, and after there were whispers of his having been a spy for the Japanese, he tried to go on the offensive and sue for defamation of character, but that quickly went away after the Foreign Office let him know that it was hardly defamation of character when they had so much evidence against him.

In 1932, only six years after he admitted breaking the Official Secrets Act of Great Britain, Sempill became a technical and business consultant to the Mitsubishi Heavy Industries until 1936, representing the Japanese company in Europe.

Mitsubishi Heavy Industries was the largest private company in Japan, building ships, airplanes, heavy machinery and railway cars. It was also heavily involved in construction contracts for the Imperial Japanese Navy.

When WWII began in 1939, Sempill – the chastised but never truly punished traitor – was given a position in the Department of Air Material which gave him access to sensitive and secret information about the latest British aircraft.

Really? Who watches the watchmen?

MI5 was still watching, but waited until June of 1941 when it learned via intercepted messages between London, Mitsubishi and Field Marshal Yamagata’s Tokyo headquarters: “In light of the use made of Lord Sempill by our military and naval attaches in London, these payments should continue”.

Sempill was still passing secrets to the Japanese, and was being paid for it.

MI5 learned that Sempill was passing on top secret information about Fleet Air Arm (the branch of the British Royal Navy responsible for the operation of naval aircraft).

While no one wanted to take down a British Lord, he was warned to stop.(‘alt or I shall say ‘alt again.)

At around that time in 1941, a Japanese business man named Makahara was arrested on suspicions of spying. Sempill visited the police station where he was being held and spoke of the man’s innocence and character – and Makahara was released a few days later.

But wait… it gets worse!

In August of 1941, British Prime Minister Winston Churchill and U.S. President Franklin D. Roosevelt held a secret meeting in Newfoundland, Canada (okay – Newfoundland didn’t actually join Canada until 1949 – it was a separate nation at that time), aboard the HMS Prince Of Wales battleship.

Though Japan had not yet officially become involved in WWII, both the U.S. and Great Britain wanted to talk over the possible military threat of Japan.

Of the discussions, aside from Churchill and Roosevelt, only two other possible people could have known what exactly was said: Commander McGrath and Lord Sempill.

Why was this a big deal?

Well, the Bletchley Park code breakers discovered some interesting details going from the Japanese embassy in London back to Japan.

(PBS is currently showing a 3-part series called The Bletchley Circle – about some of the codebreakers solving a serial killer mystery a few years later. I saw the first episode last week – which is what inspired me to look into this whole story.)

Anyhow – Churchill was informed of the transmitted code, and wrote that the contents were “pretty accurate stuff.

By October of 1941, more notes from Churchill’s personal agenda were discovered to have been sent to Tokyo by the Japanese Embassy in London.

Churchill, on October 9, 1941 says of Sempill: “Clear him out while time remains.

The Admiralty told Sempill he must either resign or be fired, but after an official protest by Sempill, Churchill backed down for perhaps the first and only time in his life: “I had not contemplated Lord Sempill being required to resign his commission, but only to be employed elsewhere in the Admiralty.

Sempill was posted in the North of Scotland, away from London and the Japanese Embassy.

On December 13 – six days after Japan attacked U.S. soil on Pearl Harbor, Hawaii (not yet a U.S. State, but still a U.S. protectorate) – Sempill’s office was raided.

His office still contained documents – secret documents – that should have been returned to the Admiralty three weeks earlier.

Showing his stupidity, Sempill was caught two days later making various telephone calls to the Japanese Embassy in London.

Confronted finally, it was agreed that Lord Sempill would retire from public office – proving that the rich and elite are treated differently from everyone else.

Sempill died on December 30, 1965.

So… if you have been paying attention… Great Britain was originally involved in helping its WWI ally, Japan build up its navy – specifically its aircraft carriers, of which it had none until 1920.

A British spy was supplying the Japanese with lots of key information about planes and other navy equipment.

Said spy was known to the British Government for many years, yet was repeatedly put in positions of power whereby he could abuse that trust.

British spy organizations knew he was communicating with Japan.

Great Britain also knew he sent Japan TOP SECRET information about a meeting between the British Prime Minister and U.S. President just months BEFORE the attack on Pearl Harbor.

And… just know that when the Japanese Mitsubishi Zero aircraft attacked Pearl Harbor, they took off from aircraft carriers built with knowledge attained from its friendship with Great Britain.

And I learned all this because I was curious about the actual history of a television show. And television rots your brain… riiii-iiiight. Me watch many TV hours every weak.

In this case, I was very disappointed in having learned some new history.

Andrew Joseph

About mreman47

Andrew was born in London, UK, raised in Toronto, Canada, and cavorted in Ohtawara, Japan for three years. He is married, has a son and a cat. He has over 35,000 comic books and a plethora of pioneer aviation-related tobacco and sports cards and likes to build LEGO dioramas. He has written and been an editor for various industrial magazines, has scripted comic books, ghost-written blogs for business sectors galore, and hates writing in the 3rd person. He also hates having to write this crap that no one will ever read. He works on his Pioneers Of Aviation - a cool blog on early fliers - even though it takes him so much time to do. He also wants to do more writing - for money, though. Help him out so he can stop talking in the 3rd person.
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1 Response to British Aviation Pioneer Spied For Japan

  1. Pingback: Want a real spy scandal? How about the aristocratic Conservative spy who was NEVER prosecuted? | Pride's Purge

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