Steven Drewett

 — often credited outside Doctor Who as Steve Drewett and sometimes credited as Stephen Drewett — was the visual effects designer for Meglos and The Two Doctors.

In addition to his Doctor Who work, he also was a visual effects designer on The Tripods, the 1981 version of The Day of the Triffids and Blake's 7.

As documentary subject
Drewett was a main interviewee on DOC: The Scene Sync Story, where he explained how Scene Sync was used to help make Meglos, as well as the utility of Barry Letts as an advocate of new technology.