Audio Transcript:

Aaron Schachter: In 1941 Japan's attack on Pearl Harbor dealt a devastating blow to the US Pacific Fleet. More than 2,000 Americans were killed. All eight US Navy battleships in the harbor were hit. Four were sunk and 188 American aircraft went up in flames. A BBC TV documentary sheds new light on just how the Japanese were able to carry out the deadly assault. Newly uncovered document show how some British officials passed on secrets that allowed the Japanese to carry out the attack. Paul Elston produced and wrote the documentary.

Paul Elston: Well not a lot of people know this but in the early 1920s there was a British air mission to Japan. And it was semi-official at that time, so what they doing from 1920 to '22 was not illegal but they were basically training the Japanese how to use aircraft carriers, how to fly on and off the decks of carriers, how to sink ships using torpedoes in port and bombs from the air. However, under American pressure, Britain, which it had an alliance with Japan up until that point ended that alliance. What's really interesting about these guys is they obviously formed very strong links with the Japanese and they carried on supplying them information and technology long after it was illegitimate. In fact, one of the guys who was called ââ?¬Å?Rocklandââ?¬  was actually spying on the American fleet at Pearl Harbor for the Japanese filming the American fleet in the run up to Pearl Harbor.

Schachter: Where they looking for money? What is idealism? Any understanding of why they were doing this?

Elston: They were certainly being paid. We know that. But I think there was a strong ideological link, certainly in the case of this British Aristocrat, Lord Sempill was his name. He developed an affinity with the Japanese but he also had an affinity with right-wing militarist regimes. He was anti-American. He would belong to the membership of a couple of fairly unpleasant British organizations that were pro-Nazi, and, in a word, I think he thought Britain was fighting the wrong war. That Britain shouldn't be in a war against Germany, and it should be in a war in alliance with Germany and Japan against Russia.

Schachter: Is there any indication of what difference this intelligence made in the war? Is this attack on Pearl Harbor or no attack? Is it that big a deal?

Elston: You must remember Japan didn't have a single aircraft carrier in 1922. By 1930 they had a fleet equal in size and strength of the Royal Navy. They did in seven years what it should've taken 10 and 15 to do. It's absolutely unimaginable that Japan would've been able to conduct that attack in December 1941, without British help, and without help from those people, specifically the ones that we've uncovered in this film.

Schachter: Were the Englishmen ever punished for passing these secrets along?

Elston: One of them was. He was in interned, although never formally charged and had his case at a court of law. The other one, Sempill was never touched. He was given warnings on many, many occasions but he was never charged or prosecuted.

Schachter: Why wasn't more made of this incident at the time? Why has it taken so long to uncover this information?

Elston: Can you imagine how embarrassing it would've been during the Second World War to have put a British serviceman or perhaps British servicemen in the plural on trial for passing on information to the Japanese. It just would've created a huge furor in Britain and America. And goodness knows what damage it would've done to the Anglo-American relationship.

Schachter: Paul Elston produced a new BBC TV documentary about British servicemen who passed on secrets to the Japanese part in World War Two. Paul, thank you so much.

Elston: Thank you Aaron.