In 1985 the flying squad was looking for a gang of armed robbers who were strapping remote-controlled explosive devices to their victims. A 14-year-old saw Crimewatch and gave police information they could scarcely believe. It led to eight months surveillance, threw up the names of some notorious London criminals and led to the arrest of the gang. The case made criminal history when one of the robbers, Donald Barrett , turned supergrass for the second time. The handling of a double supergrass posed new problems for the officers close to Barrett and to those in charge of the investigation.