The announcement usually advises that even regular fliers, should listen and watch the announcement, as it differs from aircraft to aircraft. I have flown on Easyjet, and they demand you put down books and papers, and remove headphones for the safety briefing.
Maybe there needs to be a more strict approach to this, and also to advise the passengers of the fact crew can give instructions that are “the law”. I know on some flights aboard US registered aircraft they often cite FAA law, and that you must obey crew instructions.
Hopefully when a review is done from this incident, lessons will be learned so next time, things will be different, as it may have been if this 777 was full.
Once again well done BA crew.