I was 9 and remember it vividly. Cemented my nascent support for Saints, inherited from dad.
Only bad thing was I was round a friend's house watching it and they were all Man U.
How i gloated though.
In those days the Cup Final was utterly MASSIVE, far, far, far more than today, and the TV build-up on matchday reflected that, starting several hours beforehand, non-stop till kick off.