In travelling back from Istanbul, I was reminded of Steven Runciman, the great historian of the Crusades, who spent the second world war as Professor of Byzantine Art at Istanbul University, after serving as press attaché in Sofia on the recommendation of his pupil Guy Burgess.   He used to say that to be an effective historian of the Crusades it was necessary to have mastered seventeen languages, which he had, having learned Greek and Latin by the age of six.