Think I'm a similar age to you but I know that in 1971 T Rex were the biggest band in the country. My dad was a big fan of theirs and I got quite into them when I was a kid (despite Marc Bolan tragically dying 3 years before I was born). In fact looking at the discography, at the time of this concert Get it On would have been at Number 1 in the charts, and earlier in the year they'd been at number 1 for 6 weeks with Hot Love. So it must have been a pretty big deal at the time