polygonum wrote:

A few weeks ago I noticed video (children's cartoons) on a screen in the
back of, IIRC, some form of 4X4 on the M25 in the dark. It struck me
forcibly that I could not remember ever seeing that before. Suspect
someone who didn't know what they were doing simply put it too high on
the seat back.

Plenty of the factory-fit screens for rear seat passengers fit into the
headrests of the front seats.