Thanks for the links! I'm not entirely sure whether I just transmuted one of those (although never S&S, of course!) into the more well-known one, or whether I've merged your general interest into someone else's actual review. But I think I can live with the mystery!

Fair enough! I hope you like it when you do.

It's one of those things on my list!

Although he wrote a much earlier play about time and ghosts and places that is long-lost, which I would very much like to see - it starred James Maxwell! I think they did at least try a radio performance of the script: https://ayearinthecountry.co.uk/nigel-kneales-lost-visions-and-a-library-of-voyages-into-the-unknown-ether-signposts-2352a/
https://bleedingcool.com/tv/the-road-the-legacy-of-nigel-kneales-legendary-lost-tv-play-lives-on/