AlanM,
It was as you suggest. I think you know who I am and will appreciate that I've been at this old game for decades. I can honestly say that I've not come across the Northolt solution before despite numerous pop concerts, sporting events, public demonstrations and so on.
Nevertheless I was very grateful on Sunday and my appreciation of your (collective) efforts is not dimmed by learning it's not new to you guys.
Thanks again
Uncle Ian