Spectator Seats on 5m Poles

Hello,

My name is John and I have been a motor racing fan since the 1960s.
Sorry for my first post to be such a strange one but this has been bugging me for some time.
During the late 60s or early 70s, on televised motor racing, either F1 or F5000, I remember seeing spectators using seats at the top of 4/5 metre poles.
Presumably they owned these and had driven a base spike into the ground, then attached the rest of the pole and seat.
They climbed the poles to get into the seats.
I have told my son about these but have been totally unable to find any reference to them on the internet. I wanted to show him a picture as I don't think he quite believes me.
Does anyone on here remember these please?

Thank you, John.