I came upon it by accident. I was searching through shelves looking for something else when it caught my eye. But there it was, a huge, thick, hard-backed, red book – with a metal swastika on the front.

At the time I was accompanied by a photographer from the Discovery Channel and we were carrying out research for a documentary.

As the Press officer for the Royal British Legion, my job is to protect the reputation of the organisation. But at that moment I was torn. Should I ignore the book with the Nazi emblem that looked so out of place in the Royal British Legion headquarters? Or should I open it?

Curiosity got the better of me. The book fell open on a page that showed me an image that would shock many. There was the leader of Nazi Germany, Adolf Hitler, meeting the man who was chairman of the British Legion in the run-up to the Second World War, Major Francis Fetherston-Godley.

What were the British Legion – British ex-servicemen from the First World War – doing meeting Hitler?...