Al Sinclair

 was a police sergeant who had worked on the police force for at least 10 years. He took the Third Doctor to the morgue to observe an autopsy. He discovered that Jane Broadbelt wasn't there and became worried. He revealed that he was Alistair Gordon Lethbridge-Stewart's informant and that there might be a cover-up. He helped to defend Liz when the Grestrenor attacked. Later he was almost disintegrated by the Helt and became badly burnt. (AUDIO: The Annihilators)