One is a hefty three-volume tome renowned for its groundbreaking analysis of Leon Trotsky. The other is the tale of a boy who suffers the unusual fate of being squashed flat.
Flat Stanley, a children's character invented by an American journalist, and Isaac Deutscher's 1958 biography of Trotsky would seem to have little in common. But they were brought together yesterday in unlikely circumstances after it was revealed that they are both important influences on the Prime Minister.
Tony Blair revealed the unusual pairing when he was asked for his favourite reading matter at an event to launch World Book Day in London. Speaking at the Commonwealth Club, Mr Blair said: "There were people who got me very involved in politics. But then there was also a book. It was a trilogy, a biography of Trotsky by Isaac Deutscher, which made a very deep impression on me and gave me a love of political biography for the rest of my life."
The Labour leader did not get as far as expressing which, if any, of the ideas he had taken on board from the biography, which was one of the first works comprehensively to demolish Soviet efforts to airbrush Trotsky from the history of the Russian Revolution.
But when it comes to the literary work which he picks up most frequently when not preoccupied with matters of state, Mr Blair favours the adventures of Stanley Lambchop.
The protagonist in a series of books written in the 1960s by Jeff Brown, about a boy reduced to a wafer-thin shadow of his former self and condemned to wander the world by sliding underneath closed doors, is a favourite of Mr Blair's youngest son, Leo.
Mr Blair said: "My association with books has continued through the rest of my adult life but particularly with my children. Even now with my five-year-old I know more about Flat Stanley than ever I really wanted to." It was unclear whether the vote for Flat Stanley was an attempt to shore up Mr Blair's standing with the American public. The children's character has undergone a renaissance in the United States, where he is the public face of a popular education campaign encouraging children to write letters to each other.
Shortly after entering Downing Street, Mr Blair listed his favourite childhood reads as C S Lewis's Narnia books, Robert Louis Stevenson's Kidnapped and Tolkien's The Lord of the Rings. He says he has also read the Koran three times.
But the book he has claimed most often as his single favourite is Sir Walter Scott's Ivanhoe, a work which focuses on a wounded political leader who risks being eschewed by his brethren while manoeuvring to maintain power by making unsuitable alliances.
PM's populist pronouncements
MUSIC: Friends of Tony Blair at Oxford say his favourite bands were the Rolling Stones and Led Zeppelin. But when questioned on BBC Radio 1 a few years ago he had brought his tastes up to date. He had a fondness for U2, the Foo Fighters and Coldplay, courtesy of his children. The first single he bought was the Beatles "I Want to Hold your Hand", at the age of 10.
TELEVISION: Mr Blair made an appearance on his favourite television show, The Simpsons, in 2004. In the early days of his leadership, he threw his weight behind The Sun's Free Deidre Rachid campaign even though she was a fictional Coronation Street character.
FOOTBALL: Mr Blair has revealed that his passion for Newcastle United goes back to the 1960s. But when he was pressed on the names of his favourite Sixties players, he failed to remember any. His heroes, he said, were Malcolm Macdonald and Jackie Milburn. The latter played his last game for Newcastle United when Mr Blair was four years old.Reuse content