 In 1989, shortly after his retirement, he co-wrote the Hetherington-Chalmers Report with former Scottish Crown agent William Chalmers, which examined ways to prosecute suspected war criminals living in Britain for "crimes of murder, manslaughter or genocide committed in Germany and in territories occupied by German forces during the Second World War," over which British courts did not then have jurisdiction.The report followed a 15-month inquiry in which allegations against 301 suspects were investigated.The report's recommendations led two years later to the War Crimes Act 1991, which was passed over objections of the House of Lords using the Parliament Acts 1911 and 1949.