It is a moment for which Britain has been in solemn preparation for years. Multiple official agencies were brought together. Meticulous plans were secretly drawn up. Intricate logistical technicalities were ironed out. A route was carefully mapped out.

(SOURCE) https://www.cnn.com/2022/09/15/uk/the-queen-queue-lie-in-state-gbr-cmd-uk/index.html