Thanks for that – and sorry not to reply before (only just found the comment). Seeing Roger Marshall’s name on the credits I always knew I was in for a good episode – Mandrake, The Hour That Never Was, Dial a Deadly Number, Silent Dust, The Danger Makers… to name just a few. He must have written around a quarter of the wonderful season 4? What an extraordinary hit rate. I think his stories exemplified that balance between tight plotting and novelty.