The compositing of the various images that made up the space station shot was achieved using an optical printer – a device consisting of one or more film projectors linked to camera, allowing strips of film to be re-photographed and combined into one image. By using black-and-white mattes, previously filmed elements can be inserted into new footage.
Here, Peter Tyler details the process required to film the sequences in The Trial of a Time Lord where first the TARDIS, and then the pods (containing Melanie and Glitz) are drawn into the vast space station. In the latter instance a single pod model was shot twice, to make it look as if there were two. Filming took place in the week commencing 21 April 1986: