Harry Sullivan

One of the Fourth Doctor's companions, and Surgeon-lieutenant of UNIT.  The Brigadier entrusted the Fourth Doctor to his care just after his regeneration.  Harry helped him and Sarah Jane fight the Scientific Reform Society and Professor Kettlewell's Giant Robot.  He then accompanied the Doctor and Sarah in the TARDIS, and fought against the Wirrn, the Sontaran Styre, the Cybermen on Voga (at which time the Doctor proclaimed that he was as "imbecile").  He was present when Davros created the Daleks.  After fighting the Zygons, he chose to remain on Earth.  He helped the Doctor again against the Kraals, who had made an android duplicate of him.  The Brigadier later told the Fourth Doctor that Harry had been seconded to NATO, and was involved in a secret operation at Porton Down.