I can’t speak for LNER but Avanti West Coast use a video interview system called Launchpad that sounds very similar to what you have described. It seems to be an external IT programme purchased by Avanti that has an American woman doing the introduction and taking you through the process. You tend to get a practice question that you can re-record.
You then move on to three competency based questions when you get a 15 second countdown to think of your answer, before being allowed up to two minutes to provide a decent enough answer. Unlike the practice question, you can’t go back to re-record your answer if you ‘fluff’ it.
Treat the video interview as a traditional interview - wear something smart (even though you are not leaving the house), find a suitable room and make sure there are no distractions like children/pets. I would also urge you to do the interview during the daytime when there is plenty of natural light.
I’ve done a couple of these video interviews myself and it is not an experience I enjoy as I would much rather interact in a ‘face-to-face’ scenario. I simply struggle to talk to myself in front of a recorded camera. Like I said, the LNER version may differ from the Avanti one, so please just bear this in mind.
Good luck anyway.
CJ