@Grandmabatty, you’ve reminded me of the old B&W ‘The 4.50 From Paddington’ with Margaret R. There used to be a still from it on the cover of the old paperback. I now have a yen to see it again!
I often used to think that AC must have got the idea after being on a train at night (in the days of closed compartments),seeing another train pass very close by, all lit up, and thinking, ‘What if...?’
I also always loved Margaret R as the medium in Blithe Spirit.
A young American niece absolutely adored that film - had to watch it (an old VHS copy) every time she visited.
I now have a yen to watch that again, too!