In a city of shrines the tomb of Ilm Din is one of Lahore’s most popular. Hundreds of Pakistanis from all walks of life file through its elegant marble enclosure each day. Doctors, lawyers and street vendors rub shoulders as they say their prayers and heap rose petals on the grave of an illiterate 19-year-old executed for murder.

Ilm Din’s crime is detailed in a copy of a police report, enlarged to cover one of the walls next to his grave: on 6 April 1929, in Lahore’s old city, Ilm Din stabbed to death Mahashe Rajpal, a Hindu who had published Rangeela Rasool, a lurid biography of the prophet Muhammad. The mullahs of British India had been agitating against the scurrilous book for five years but legal cases against its publisher had failed.