Brian Hayles created the Ice Warriors and The Celestial Toymaker, and also had a prolific non-Doctor Who career, script-editing The Archers for a while and writing episodes of Doomwatch, Out of the Unknown and Z Cars. He died more than thirty years ago, so in-depth interviews are somewhat thin on the ground. This is what I’ve managed to find so far, but if anyone has anything else and wouldn’t mind sharing it, I’d love to see some more Brian Hayles interviews!
“I wanted to keep the Toymaker very vague, I didn’t want to explain exactly who he was. At the time, I had grand visions of his becoming like the Daleks, coming back again and again, and then of course something very like that happened a few years later with the Master.
“The Ice Warriors were never intended to return (after their first appearance), but I think at some stage it was decided to try them out again as possible recurring villains. I think there would have been more stories featuring them, had it not been for the big change when Pat Troughton left. Barry Letts and Terrance Dicks came in and wanted to get away from the past, which I think was a very wise move. I was very surprised when they decided to bring them back after a few years.
“I had to evolve a new landscape in terms of inventing a civilisation called Peladon. It wasn’t evolved as a saga, although in fact it could well have developed that way, because the planet had a history behind it – in my mind, at least. The original was going to be a one-off called ‘The Curse’. If you followed the psychology of the Ice Warriors, they were still basically the same people. The Doctor accepted their help very reluctantly, because he knew they could turn nasty at the drop of a scale or something.”