I'm going to stick my head above the parapet here at the risk of hate, but I was one of the ones who clapped. Not through disrespect, but just because I both totally forgot it was a minutes silence straight after, as well as being sucked in to it with others doing it. Once I remembered I stopped immediately
I know people shouldn't need to be reminded of the protocol, but we're human and either make mistakes or just don't know. The fact there wasn't a single disturbance during the last post and even for the brief time the silence was adhered to shows people wasn't disrespecting the meaning behind it all.
I genuinely don't know if it was announced of the procedure, but I definitely didn't hear it. I don't think there is any harm reminding people of it though over the tannoy if they get the quality better. There will be loads of youngsters who won't have a clue.