Purely on a point of pedantry, it was not the first time that "Star Spangled Banner" had been played at Buckingham Palace, but at the specific instruction of the Queen it was played before the UK National Anthem, a completely unique breach of royal protocol.

For what it's worth, we will be observing the 3 minutes silence at work today, and people are queuing to sign the book of condolence that has been made available in the Mayor's Parlour. Tomorrow across the UK all football and rugby matches will be preceded by 3 minutes silence, and all players will wear black armbands.