I left dissatisfied but then fate, or rather the Metropolitan police, intervened to provide a living supplement to the exhibition. Within eight paces of the entrance to Taking Liberties two officers, a man and woman, had stationed themselves inside the library and without the slightest sense of irony or trespass were stopping people to ask their names, contact details and height under terror laws.
I would have taken a photograph with my phone but that has been made illegal so I watched while a stream of utterly ordinary-looking people were questioned. I asked one man whether this was usual in the British Library. Yes, he said, it was well known that the police used the library as a convenient means of boosting their stop and search quotas and balancing the number of black and Asian people stopped in the street with the white people in the library.
I cannot say whether this is true but I saw nothing to disprove it while I looked through the postcards. He added that the police favoured the library because at the entrance everyone's bags are given a cursory search. So the police had only to stop people, not search them, and this saved time for a pair of busy constables who were clearly in a hurry to get the names in their notebooks and move on.