“John Buchan’s 1915 action novel has been filmed at regular intervals, following Alfred Hitchcock’s classic version with Robert Donat as buccaneering hero James Hannay. Buchan was famously inspired to write the novel by his daughter counting the stairs of the nursing home in Broadstairs, where he was convalescing. He turned the phrase into a key mystery of the novel, and Hannay’s eventual discovery of its meaning (it is the number of steps down a cliff path to a waiting yacht) helps keep Britain’s military secrets intact from the Germans.
Hitchcock significantly changed Buchan’s plot for his 1935 movie, writing a climactic music hall scene in which ‘Mr. Memory’ is asked ‘What are the 39 Steps?’ and is about to reveal the answer (‘The 39 Steps is an organization of spies collecting information on behalf of the foreign office of…’) when he is shot dead. An equally evocative twist was introduced in the 1978 film starring Robert Powell, where the thirty-nine steps turn out to be the number of stairs in the clock tower of Big Ben.”
Excerpted from: Rogerson, Barnaby. Rogerson’s Book of Numbers: The Culture of Numbers–from 1,001 Nights to the Seven Wonders of the World. New York: Picador, 2013.