Michael Pembroke

 was a scientist who created a temporal accelerator, a device that could transport objects instantaneously, in 2003. He managed to circumvent the Heisenberg uncertainty principle by using the Vacuum Effect. He questioned the Seventh Doctor about the dimensions the Scourge lived in. He went with Ace to the Doctor's TARDIS, on the roof. The Doctor managed to communicate through him. (AUDIO: The Shadow of the Scourge)