MI5 managed to get a British spy to infiltrate Adolf Hitler’s inner circle just days before the outbreak of the Second World War, a new book has revealed.

The story of the agent, codenamed M/T, has been told for the first time in a book about Maxwell Knight – a senior MI5 spymaster during the 1930s.

Kathleen Tesch, the agent selected to get close to the Nazi leader, was not the likeliest of choices. She was a Home Counties housewife and a lover of dogs who was known among friends for the inventive costumes she wore at the local village fete.

She had been working for MI5 for less than a year when she was asked to travel to Nazi Germany under cover of being a member of a British fascist group called The Link.

Ms Tesch successfully managed to meet Hitler at his Eagle’s Nest hideout high in the German Alps. In passages quoted in the book, she reveals her shock at being summoned to meet the Nazi leader.

While her party was admiring the view of the Eagle’s Nest, two soldiers boarded their coach and began calling Ms Tesch’s name. She was apparently chosen to meet Hitler because her surname carried a lot of prestige in Germany at the time.

“I must admit that for a moment I got a bit of a fright,” she wrote. “I was asked to come out of the coach, which I did, and was then taken up to the house and inside; after waiting in a room for a while I was taken into another room where Hitler was sitting in an armchair.”

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She described the Nazi leader as looking older and more haggard than in photographs.

The encounter did not reveal a trove of Nazi secrets, however, and Ms Tesch said Hitler seemed to be barely aware of her presence.

“Hitler seemed to be quite unaware that I was in the room”, she wrote. “A good deal of the time was spent in complete silence, which I tried to break by making such idiotic remarks as ‘What a very beautiful view’.

“To be candid, I felt rather uncomfortable, not because of the importance, but because they seemed to know very much more about me than I did about them!”

In the end, Ms Tesch ended up leaving the encounter with little more than a signed copy of the German Fuhrer’s book, Mein Kampf.

The story is revealed in a book about Mr Knight by Henry Hemming, titled “M: Maxwell Knight, MI5’s Greatest Spymaster”. Many believe Mr Knight, who was known as M, was part of the inspiration for Ian Fleming’s idea of James Bond’s boss.