In June 1940 Hitler's next target was Britain. And whilst the vast majority of Britons would do anything they could to resist the invasion of Britain by Nazi Germany, there were some who not only would welcome such an attack, they were actually dedicated to helping to make sure of a German victory over their own country, so virulent was their antisemitism.
They were apparently ordinary Britons living seemingly ordinary lives, working in shops, offices and factories (some were even involved in important war work) but unknown to their neighbours and some friends and relatives, they were, in reality, dedicated to promoting the cause of Nazism in Britain and to helping sabotage the British war effort.
However, what they did not realise was that every move they made, every contact they undertook with their German 'spymaster' was actually all taken under the careful control of Eric Roberts, one of the most experienced and dedicated MI5 agents of his generation.
Formerly a bank clerk from Epsom, Eric Roberts had spent the years before World War Two dedicated to rooting out Communist infiltrators and members of the British Union of Fascists.
But at the onset of the Second World War, he became known as Agent Jack King and was given the dangerous task by spymaster Maxwell Knight of seeking out potential traitors and convincing them that he, Jack King, was a Gestapo agent.
It was called Operation Fifth Column and none of the traitors were ever aware that, rather than working for the Gestapo, they were actually working for MI5.
Jack King, working virtually by himself, built up a network of hundreds of Nazi sympathisers and was able to neutralise the impact that their treasonous behaviour would have had, should they have been recruited by a genuine Gestapo agent.
How did he do this? Eric Roberts had an amazing ability to convince people to place their trust in him.
Robert Hutton's book is very well researched and very well written and it casts a strong light on a hitherto unknown part of World War Two.
Why was it kept secret for so many years after the war? Hutton reveals these reasons.
This book is a must have for students of war history and the general reader.
It's published by Weidenfeld & Nicolson and the published price is £9.99, although it may be available for less on Amazon (check out the Amazon link to the right of book reviews) and other stores, also available as an e-book and an audio book.
I can heartily recommend this book as a must read.