We started with photocopied roundels on cardboard walls - and some scenes still show those (!). It was a good cheap way of constructing a set and did the job for the time. The image above shows the "wardrobe room scene" later dropped from the edit.
With the advent of the Jon Pertwee filming we decided to "upgrade" and so Ashley designed some new ones - with him and Stephen constructing 7 new walls for that scene. As the filming time grew near the rest of the team became involved in the construction. Here we see Ian at work cutting out the roundels, whist in the picture afterwards he is seen surveying the work; walls being laid out to dry on Stephen's driveway.