Your first choice focuses on the three-times prime minister Stanley Baldwin, who dominated politics in the interwar years.

This is a doorstop of a book. It is a definitive biography by Keith Middlemas and John Barnes. It replaced the official biography written by GM Young 17 years before, which came out in 1952. It painted him in a much more sympathetic light and was far more understanding of the importance of his role. They used a wealth of documents and oral history. It was a milestone biography that never perhaps achieved the recognition that it should have done. It brings this extraordinary man to life and puts him in the right place.

What do you think distinguished Stanley Baldwin as a politician?

He restored calm to the nation after World War I, after the uncertainties of postwar economic hardships, the rise of dictators. Here was the man who piloted the Conservative Party into a direction of democracy and acceptance of its moral responsibility for the whole nation and not just for the well-off in society. He helped school Labour in the ways of parliamentary democracy. He brought calm to the nation at a worrying time. He was the first radio and film prime minister. He popularised the modern role of the prime minister. And he steered the country through, as we saw in the film The King’s Speech, the perilous waters of the abdication [of Edward VIII].

Your next choice, Lloyd George, is in four volumes written by John Grigg, who is regarded by many as one of the greatest political biographers of the 20th century.

I think what is special about this biography is John Grigg himself. He was the son of Edward Grigg, an eminent figure in Britain in World War II, who was in Churchill’s wartime government. John Grigg went on to forsake his own membership of the House of Lords when his father died. He was an important figure himself in politics. He was a prominent critic of the Suez Crisis. He had this real insider’s understanding of politics, which is what makes him such a good biographer. He also wrote very elegantly. He managed to be a great literary biographer.

What made this work about Lloyd George particularly compelling?

I think the insight into the politics of the period around Lloyd George and the quality of his own writing. He won the Whitbread Award for the second volume and he won the Wolfson Prize for the third. He was this combination of someone who grew up with politics at a very early age in the world of his father and then in his own right. He used all that understanding to write extraordinary biographies in a very polished and fine style.

Is there one particular aspect of Lloyd George that you understood better from reading this work?

I think it shows his humanity. The closer you get to people the more you realise that simplistic judgments are naive.

There have been so many books written about Winston Churchill – what made you choose Martin Gilbert’s?

I remember when I was a very young researcher going to interview Martin Gilbert at a house he had in west London and going down to his basement. There were a lot of shelves in this vast basement and every shelf was piled with documents about Churchill’s life. It was the excitement of being with somebody who was so determined to get every single fact right.