Guest Stars Lynda Bellingham as The Inquisitor Michael Jayston as The Valeyard Malcolm Tierney as Doland Honor Blackman as Professor Lasky Yolande Palfrey as Janet David Allister as Bruchner Sam Howard as Azta Arthur Hewlett as Kimber Denys Hawthorne as Rudge Michael Craig as Commodore Travers Leon Davis as Ortezo Simon Slater as Edwardes Barbara Ward as Ruth Baxter Peppi Borza as First Vervoid Bob Appleby as Second Vervoid Uncredited Robert Goodman as Hyperion III Officer Richard Bonehill as Hyperrion III Guard