And that is the issue adrianjc32. That it was done without a word being said to the pax at the front of the queue. A polite "excuse me, I need to take these passengers ahead of you, my apologies" and done with a smile would have worked wonders.
It sounds like this BA staff member simply breezed their way in front of a queue of passengers without extending even basic courtesy to those that had been waiting patiently in line. I don't think anyone could condone that.
Agree completely ... extremely poor practice. I would hope there is some BA guidance as to how it should be done, and that doesn't look like it.