“Before it was made into a hit West End play, before it was bound for Broadway, before it was set to be Steven Spielberg’s next big movie, War Horse was a slim, powerful children’s book … Published in 1982, the book was a ‘huge nonevent’ at the time, according to its author, Michael Morpurgo … ‘If sales ever reached 1,500 copies a year, I would be surprised’.”