Little parade on Garden Row

Does anyone know the reason for the sweet parade of youngsters on Garden Row earlier this afternoon. Little ones singing and waving various flags. It was clearly a planned event, given that there were parental and community support escorts. I enjoyed seeing them pass by, but I don't know what was being celebrated.

I got a Mexican wave from youngsters as I was cycling near Lambeth North yesterday... There were loads of kids on the pavement.