it caused a buzz of excitement.

Signed "Joe K'' and addressed to a Herr Lothar Frederick in Berlin, it carefully noted the comings and goings of ships in New York harbour.

There were details, too, about weaponry.

Like all wartime mail from America to Europe it had been flown to Bermuda to be scrutinised for possible secret messages.

To Sir William Stephenson, First World War flying ace, inventor, businessman and the brilliant mastermind of Britain's North American intelligence operation, the alarm bells were ringing.

His suspicions were soon heightened with the arrival of more "Joe K'' letters.

And they later proved well-founded after the men behind the letters were tracked down.

The "Joe K'' trial in the United States, and the smashing of a German spy-ring became big news in 1942.

As many as 300 documents were exhibited at the five-week hearing, and witnesses were called from Bermuda. It ended with eight German agents being jailed for operating out of America.

The Berlin address turned out to be a cover for Gestapo chief Heinrich Himmler.

To Sir William, chief of British Intelligence in New York in the Second World War, it was a coup.

And his triumph is now being recorded by retired CIA officer Mr. Thomas Troy, who has been in Bermuda researching for a book.

The book, "Sir William'', is sub-titled "British Secret Intelligence in New York in two World Wars''.

It features two Sir Williams -- Sir William Wiseman, chief of British Intelligence in New York in the First World War, and Sir William Stephenson, whose cloak-and-dagger exploits were the launch-pad for the book and film "A Man Called Intrepid''.

Mr. Troy was a close friend of the second Sir William, a Scots Canadian who lived in Bermuda until his death in 1989. He was in his 90s.

One chapter of the planned book -- expected to take a year and a half to complete -- will be devoted to the Bermuda link of the censorship and intelligence operation.

In particular, Mr. Troy wants to find out about the nerve-centre of Sir William's activity -- Hamilton's Princess Hotel.

A science and testing laboratory was set up in the basement.

It was there dozens of experts in inks, glues and paper sifted through stacks of mail. Decoders were on hand to unravel secrets.

"It was a very sophisticated operation,'' said Mr. Troy, from Maryland, who was in the CIA for 30 years and has written a book about the organisation.

"Unfortunately I am unclear as to the lay-out of the science and testing laboratory and would love to speak to anybody who was there at the time, or could provide information.

"This laboratory was the most important part of the Bermudian operation.'' Mr. Troy explained how pencil-thin rods were slotted into the tops of envelopes. Letters would then be rolled around the rod, examined, and then reinserted.

Another technique -- the "wet method'' -- would be to use steam to open mail.

But since steam could alter the glue, it would require great expertise to reseal the envelope undetected.

"Of course, once a secret message was decoded, it was sometimes felt necessary to insert something to misinform the recipient,'' said Mr. Troy.

"It would have to be done in such a way as to make the insertion appear part of the original. The same ink would have to be used.'' Mr. Troy said up to 300 people would have been involved in the bid to frustrate German, Italian and Japanese espionage.

Mainly Britons and Canadians, they lived in the old Bermudiana Hotel.

"Because of its location as a crown colony, Bermuda became the bottle-neck and eventually the cork which controlled the movement, especially from the western hemisphere to Europe, of all secret messages,'' said Mr. Troy.

Mr. Troy told how mail came in by flying boat which landed at Darrell's Island.

Letters would be brought to the dock at the Princess to be scrutinised before "being sent on their merry way''.

Intelligence chiefs were also on the look out for gold, coins, stamps and photographs being transferred to Germany.

They also wanted to stymie the flow of funds to help the Nazi's war effort.

Mr. Troy said the "Joe K'' trial was the most publicised success of Sir William's operation.

But there were other triumphs.

"There is no evidence that German espionage eluded censorship to the detriment of the Allies.

"There is no question the censorship was successful in prventing the smuggling of messages, stamps, and jewels of tremendous monetary value.

"The Germans had a problem in supplying funds and the British and Americans managed to control the movement of messages and goods.'' Mr. Troy said his book would relate how Sir William's life crossed paths with that of Englishman and baronet Sir William Wiseman.

"Both men were World War One veterans and had been injured in that war. They had successful civilian careers and both had successful intelligence careers in the United States.

"Not only were they both very successful men in private life as well as wartime life, but they also became best of friends.'' Anyone who can help Mr. Troy with his research can contact him at 6101 Rudyard Drive, Bethesda, Maryland 20814.

STUDYING BERMUDA CENSORS -- Mr. Thomas Troy.