Did Agatha Christie Have a Spy Inside?

That's the question the government wanted to know.

From a piece in the Guardian...

What made MI5 suspect one of Britain's famous crime writers? The answer, it can now be revealed, lay in the name of a character in her wartime novel N or M, whom she called Major Bletchley. He appears in the book as a friend of Christie's pair of detectives, Tommy and Tuppence.

In the book, published in 1941, N and M are the initials given to two of Hitler's agents as Tommy and Tuppence hunt for the enemy within. Major Bletchley comes across as a tedious former Indian army officer who claims to know the secrets of Britain's wartime efforts.

Christie happened to be a close friend of Dilly Knox, one of the leading codebreakers at Bletchley Park. MI5 was concerned that the major's inside knowledge of the progress of the war was based on what the codebreakers knew about Hitler's plans. Had Christie mischievously named the character Bletchley because Knox told her what was going on there?