Which act failed to turn up at the first Glasto Festival (which was called the Pilton Festival), I have found two answers - one that it was the Kinks as Ray Davies had a sore throat and two that Wayne Fontana and the Mindbenders didn't make it. T Rex were drafted in as they were playing nearby.
The Kinks did not appear because the Festival was billed as a 'small event', and the record label did not think it appropriate that a hit singles band be associated with anything with the word 'small' in it. So they didn't actually 'fail to turn up' - they were withdrawn - but no hard feelings, because Ray Davies played this year.