Nice thread subject!
1968, Curborough Sprint course near Lichfield, where I helped to marshal at the tender age of 9.
This experience was occasioned not by a parent, but by my primary school teacher. She was a) ravishing (even a then 9-year old recognises that a slim, attractive, young blonde bird teaching you is a bit different from the others!) b) a Lotus Elan owner c) A sprint club member. She had asked if anyone wanted to help marshal, I volunteered, and that is where it all started.
From that first event, I remember a mixed field of everything from a white road-going A-H Sprite with its lights taped heading sidweays up the inside bank on the first corner, to some brand new private Formula 5000 machinery. There was a very early production Datsun 240Z there which upset a load of the traditional British sports cars of the time around, plus plenty of specials (a Morris Minor fitted with a Jaguar engine, and a Ford Popular with a stonking big american V8 both made a firm impression) .
The sights, smells, colours, and proximity to the action, from helping marshal a corner to pushing cars around in the paddock and at the start line, are still clear, as is the sound (first) and then the sight of a dark blue Ford GT40MKIII, as it motored into the paddock......
Needless to say, I continued to volunteer to help out, and the rest just sort of followed naturally from there...
MG Mark