Trey Korte

Donald Korte the third, known as Trey Korte was an American and a friend of Melanie Bush.

When he met the Sixth Doctor, Korte was an exchange student in England. He had latent psychic powers, which his encountering the Doctor or the TARDIS (or both) awoke.

This made him useful to Martyn Townsend. His cybernetically augmented body was dying, and Korte could transfer his mind into a new body built for him by Dr Ingrid Krafchin.

However, Krafchin was actually an Auton, and wanted to use Korte to open a mental bridge to the Nestene Consciousness so they could take over the Earth. Korte was freed and the plan stopped by the Doctor. (PROSE: Business Unusual)

The Sixth Doctor, Mel and Evelyn Smythe met Korte again four years later, during which time he had been developing his powers and using them to help UNIT and C19. He was also searching for his missing lover Joe Hambidge.

He was captured by the Magnate, but not before alerting Bob Lines. Lines was able to use a device the Doctor had given him to send a signal to the Time Lord.

Korte found himself being held by the Irish twins Cellian and Ciara, who also had Joe Hambidge with them. Joe apparently had no memory of Korte, as he had been brainwashed with two other teenagers to be Nestene slaves. After the destruction of Senénet, though, the twins came to regret their actions and took care of the teenagers.

After a Cylox invasion was stopped by the Magnate, Korte and Mike Dudley, an ESPnet, told the United Nations that the ESPnets would operate under their own control, helping Earth as they saw fit.

What Korte did not know was that Hambidge did remember their time together. His mind, though, had been made unreadable telepathically from the procedures done to him by Senénet and left him emotionally stunted. He continued to feign ignorance so Korte could move on with his life. (PROSE: Instruments of Darkness)

Behind the scenes
In the acknowledgements to Instruments of Darkness, Gary Russell thanks "(the real) Trey Korte". Also, in the introduction to Placebo Effect, he thanks Trey Korte "for the theology discussions".
 * Since there is a real world Trey Korte, this may be the same Trey Korte who wrote The Schoolboy's Story.