Private Wyatt
Private Wyatt was a soldier who served in UNIT. He was one of the soldiers attached to Brigadier Lethbridge-Stewart's group supplying security for the Inferno Project. When an unexplained power increase began coming from the facility's nuclear reactor, Wyatt accompanied the Doctor, the Brigadier and Sergeant Benton to the power station to investigate.
There, the four men found Harry Slocum having turned into a Primord, knocked out John Bromley and turned up the power. Wyatt shot Slocum, but at first this didn't seem to affect him, and the transformed technician attacked and knocked out Wyatt before finally succumbing to his wounds. In the meantime, the Doctor was able to get the power returned to normal.
Although Wyatt survived, he, along with Bromley, became a Primord due to physical contact with the transformed Slocum. The two escaped from the power station and roamed the grounds. Wyatt encountered the Doctor on a catwalk, and attempted to club him with his rifle. However, he overbalanced, and the Primord soldier promptly fell to his death.
Alternate Universe
Private Wyatt was a soldier in the Republican Security Force, serving under Brigade Leader Lethbridge-Stewart. He was already a Primord when the Doctor arrived, and attacked him on top of a large gas tank. The Doctor managed to fend him off, and then Platoon Under Leader Benton and his men, who'd been chasing the Doctor, arrived, and one of them shot Wyatt, causing him to fall off of the tank to his death.
