The biggest gap in the biographies of many prime ministers concerns their use of intelligence. Histories of the postwar Labour government, for example, give no hint that Clement Attlee, at his own request, had far more private meetings with the director-general of MI5 than any other 20th-century prime minister. Books on the Blair years, by contrast, show much greater interest in intelligence. ‘Controversy over intelligence defines Tony Blair’s government’, write Richard Aldrich and Rory Cormac in The Black Door. Their pioneering book is the first to examine how all British prime ministers since the early 20th century have used intelligence. It is also a very good read.

But for the danger of further delay to his overdue report, Sir John Chilcot would do well to consult The Black Door, which puts Blair’s use of intelligence before and during the Iraq War in longer-term perspective. Among the early initiatives of Blair’s government was an unsuccessful attempt, sponsored by