How about two gigs that I did go to but didn't actually see?
Number 1: Benefit concert for Robert Wyatt at Drury Lane Theatre, London in 1974. Introduced by John Peel and featuring loads of my favourite performers. I went down to London on the train with a bunch of mates and we had all day to kill so we bought a load of vodka and sat around in a big park, having a laugh and gradually getting sloshed.
When we finally went to see the gig, I remember sitting down in my seat and hearing a big cheer as John Peel came out on stage to introduce the first act. Next thing I remember was being dragged through the streets of London back to Euston Station singing "I'm a Believer".
I was told that it was a fantastic night, I should have been there. Oh, I was - never mind! Ho ho...
Number two: Dexys Midnight Runners, Warwick University, 1980. It was before 'Geno' went to number one in the charts and none of us had heard of them. It was during the 'donkey jackets and brass phase' (none of that dungarees and fiddles malarkey!). I got bored of waiting for them to come on stage so I nipped up to the union bar and ended up spending the whole evening playing on a Space Invaders machine. I beat my hi-score but missed what my mates later told me was the best gig since, oh, the Robert Wyatt benefit in London!
