I heard later that they team had spent an afternoon filming Jon.
But when the (wonderful) documentary came out - of Jon Bentley there was nothing.
Another 'lost episode'?
But I found out what happened in this video.
Bear with the start of it; it will get to the 'Ladybird' point after a minute or two:
The fascinating Jon Bentley introduces 'The Lost Episodes' - pieces which I like very much indeed; I would love to see the originals one day.
If you'd like to see online versions, you'll find them here.