Bertrand Stewart served in the ranks of the Imperial Yeomanry during the Boer War. seeing action at Cape Colony, Orange River and the Transvaal and this seems to have given him a taste for adventure. In 1906, while working as a solicitor in London, he was commissioned in the West Kent Yeomanry, and in around 1911 said that he wanted to do “something spectacular in the way of discovering German preparations for war” and got in touch with the Secret Service
Travelling in Germany in 1911, he was arrested at Bremen and charged with espionage. It was claimed that he had been attempting to find the secrets of German naval defences in the North Sea and dockyards and was picked up after documents had been passed to him in a Bremen restaurant.
He was still reading them in the rest room when he was arrested.