I love the expression on Eric Clapton's face in this photo. He has joined Bob Dylan on stage for the encore finale at the famous concert at Blackbushe Aerodrome in July 1978. I imagine he's trying to follow the changes as Bob runs through Forever Young or whatever it was they were playing.
As well as Bob Dylan and Eric Clapton, the bill included Joan Armatrading, Graham Parker and the Rumour and a couple of bands who I have no recollection of at all, Merger and Lake.
Both Parker and Armatrading had top notch bands at that time. Here's a sample of GP and The Rumour live in 1978.
Musically, the highlight of the Blackbushe concert was Eric Clapton's set. The band were really cooking and the music had just the right mix of blues and swing. There is amateur video of it but I can't locate it right now. Here's some alternative footage from 1978.
By the time Bob Dylan came on, our group was a little more laid back and we were sat round a campfire near the back of the crowd, singing along to all the classics and the new songs from Street legal. Here is a reasonable audio recording of Dylan's set:
There's a variety of other, mostly silent or poorly-recorded footage of the day on YT, which is probably only of interest to those who were there.