Maxil

Commander Maxil was a member of the Chancellery Guard. Zealous and humourless, he stunned the Doctor and confined him in a cell under the Capitol to await the judgment of Lord President Borusa and the High Council of Time Lords. (DW: Arc of Infinity)

Behind the Scenes
Maxil was portrayed by Colin Baker, who later became the Sixth Doctor. As a result of Baker being chosen to replace Peter Davison as the Doctor, the character of Maxil was dropped from the later anniversary story The Five Doctors.

This wasn't the last time a future Doctor would be involved in an earlier production; David Tennant participated a Doctor Who audio production for Big Finish before being cast as the Tenth Doctor.