I broke my leg in 1992. When Ian came to visit me in King's College Hospital,  for my reading matter he brought me a massive volume of the Minutes of the London Corresponding Society in the 1790s. It's not everyone's kupachar. One of the notable features in it that Ian pointed out to me,  is that at some meetings of this revolutionary society, almost everyone present was later found to be a police informer. Ian and I had much discussion about this, because there's a long history of police informers. One, even two were responsible for tipping off the police and planting a gun in the home of the black Chartist William Cuffay, who was transported to Tasmania in 1848. In the 20th century the trade unions, particularly the ETU, were riddled with informers. More recently, there was the shameful scandal of undercover police amongst eco-activists.  It was typical of Ian to locate and expose the often shabby aspects of our society.