In the early 80's I used to help put up the illuminations. The tree on Fargate used to be very tall, over 40 feet. I remember one year we strung the festooning and lights around the tree using 2 hydraulic platforms, the one I had was a 40 footer and at full height didn't reach the top of the tree.
The lights and set pieces were stored at Hillsborough Barracks at that time, we used to start testing them in September, the barracks were the coldest place I ever worked in, even when warm outside it was freezing inside.
Switching on the illuminations was a team affair, at strategic lampposts an electrician would stand with the post door off waiting to throw to switch on his section. The switch on was at the City Hall, but the first thing to be switched on was the tree on Fargate and the Goodwin fountain. The 'star of the show' would organise a countdown, when it reached '1' a worker would bang on the window of he underground gents toilets in the Town Hall, where inside, someone would throw the switches to light the tree and fountain. When that lit it was the signal for the electricians to throw their switched in the lamp posts, and as each section came on other electricians would put on their bit. That's why they came on is a wave fashion and not all at once.