In the movie The Queen Tony Blair is given explicit instructions that when his audience with the Queen is over he is to leave by walking backwards.
However, in the television series The Crown there is no mention of this and people leave the Queen with their backs to her all the time.
I’ve tried to find the protocols for meeting the Queen and as best as I can tell, this backwards walk is an outdated custom, long since abandoned. So I wonder why it was used in the movie. I suspect it may have been dramatic license to show Blair’s discomfort on his first meeting with the Queen, especially since his wife was an outspoken anti-monarchist, but I don’t really know.