When I helped bring the Modern Slavery Bill to parliament I thought here, surely, was a piece of legislation that the PM would want to own. Three women — Theresa May, the Home Secretary; her then special adviser Fiona Cunningham; and Philippa Stroud, Iain Duncan Smith’s special adviser — had all worked for a Bill that would give the government a chance to seize the moral high ground, restoring Britain to its historic role as leader in the abolitionist movement.