It was a show sponsored by advertisers - these were common on Radio Luxembourg and no doubt on Amreican commercial radio, so maybe Peel had done similar shows during his time there.

Radio London was short-staffed in the final week(s) because many of the DJs (Blackburn, Skues, Everett) had left and were already working for the BBC or Luxy, while others were expecting to join the Beeb's new pop service (Radio 1) when it began. So Peel might not have wanted to do a this type of show, but had no choice as, with DJs like Mark Roman already doing 6 hours of programmes, there was no-one else available.

That explains it. I wonder how long those sponsored shows were? Were they like one hour shows?

There used to be a list of available Radio London recordings on Azanorak, which included a number of sponsored shows - maybe it's still accessible somewhere on the web. They were shorter than the standard three-hour DJ shift on the station, often less than an hour long. I can't remember hearing many of them, because most of them were broadcast in the daytime, when I was at school.

I remember listening to the show and if memory serves it was a full two hours of Stones music. The Peel Wiki page on Disc and Music Echo has this:

July 8 "Scene" gossip column: "Radio London deejay John Peel's tribute to the Stones - two hours of their music last Thursday without any reference to the court result"

That would be 29 June - the day the sentence was announced - or more correctly the early hours of 30 July, so Brian Long is probably right. May also explain why no recording of the show exists - Peel no doubt decided to respond to the judge's verdict after hearing the news earlier that day, but may not have told the other DJs on the ship of his plans.

An entire book is devoted to the Stones' drug bust and its repercussions:

https://dangerousminds.net/comments/simon_wells_the_great_rolling_stones_drugs_bust

- yet it doesn't mention Peel's tribute at all...

Sounds like the 30 June date is more of the accurate one

Yes, I think so. And Peel may also have broadcast an hour of Stones records on 4 July, as IT states - can't recall hearing that, but maybe my memory is at fault....