It offers a different perspective on how the Second World War was won, seen through the prism of the personbal interaction between Franklin Roosvelt, Winston Churchill, George Marshall and Lord Alanbrooke, the two political Masters and two military Commanders, who each dominated their own sphere. It contains the verbatim records of Churchill’s War Cabinet, which I discovered while researching the book and which have never been quoted from before.

What motivated you to write specifically about Churchill, Roosevelt, Alanbrooke and Marshall?

My first book which I began researching 20 years ago was about Churchill’s foreign secretary, Lord Halifax, and I have been entranced by the period and personalities ever since. The way the relationships between the four men interacted and changed as a result of each other, like the four edges of a Rubik’s Cube, is fascinating.

Did your initial opinion of any of these men change dramatically during your research?

Yes; previously I had thought Lord Alanbrooke was pretty much the straightforward soldier that emerges from his ghosted autobiography and diaries, but he turns out to have been a far more complex figure than that.

Of Roosevelt, Churchill, Marshall and Alanbrooke, who charmed you the most?

Surprisingly enough, George C Marshall was the man who – as I learnt much more about him, emerged as the most approachable of this formidable quartet of power. Today best known for the European Recovery Plan named after him, he was America’s top soldier from the day the Germans invaded Poland in 1939 until after final victory over Japan in 1945.

During the process of researching, what surprises did you discover?

That decisions upon which tens of thousands of men rest can be made as a result of horse-trading and hard-fought compromises, rather than simply going with the best, boldest plan as it appears at the time. There are so many instances of this in my book as to make this the rule rather than the exception.

How did you tackle such an enormous subject? Do you have a set routine in the way you work?

I am at my desk at 6am or earlier every day, because no-one phones up at that hour, thank God.
For this book, I went to my aunt’s farmhouse in the Dordogne for four weeks, stocked up the fridge, and at one point did not see a single human being for ten consecutive days

Is there a particular book or author that has had a significant influence on you as a writer?

Kenneth Rose’s biographies of Lord Curzon and King George V are for me the model biographies from all aspects of the craft.

Why are you particularly passionate about history?

Because of Mr Christopher Perry, my prep school history master, who instilled in me aged ten a profound love of the past, often by acting the most dramatic bits out of it for the class. He also insisted that we learn 100 dates from British history by heart, appreciating how important chronology is in the writing of historical narrative.