Henry Hemming is a great story-teller — and this is a great story.

In June 1940, during the ‘darkest hour’ in modern British history, when a German invasion of England seemed only weeks away, William Stephenson was sent to New York to do everything possible to encourage the United States to enter the war.

By the end of the following year, Stephenson and his team had succeeded brilliantly. They were instrumental in every stage of the gradual involvement of the US in helping to arm and support Britain. Even though it took a Japanese surprise attack on Pearl Harbor to get the US to declare war, once Germany issued its declaration of war a couple of days later, Roosevelt ordered the military to focus first of all on defeating Hitler.

There are parts of the story which make for uncomfortable reading. The British did not hesitate to feed the Americans false intelligence, including faked letters and maps. On one occasion, they got Roosevelt to publicly cite such forged materials — even though the president himself may have suspected that they were not genuine. Like the Special Operations Executive whose job it was to “set Europe ablaze”, Stephenson and his team were engaged in “ungentlemanly warfare”.

My favourite moment in the book has to be this: In May 1941 Lieutenant Commander Ian Fleming — yes, that Ian Fleming — arrived in New York and met Stephenson, who he described later as a hero and “great secret agent.” Fleming wrote that Stephenson mixed “the most powerful martinis in America.” Fleming so enjoyed the drink that he wrote down Stephenson’s recipe which ended with the words, “shaken not stirred.”