Nicks Richards explains the background to the tape in a posting on the Radio Caroline Fans Mailing list

Last Few Days of Mi Amigo / Nick Richards Mystery
From: nick richards
Date: Thu, 20 Mar 2025 09:17:08 PDT
The Mystery Tape .....
I'm happy to explain the mystery of the pre recorded tape from March 1980.
On the evening of March 19th 1980 there was a show on ITV I think, that was going to feature Janis Ian the American singer/songwriter. So before I went to bed that day, I went into the studio and recorded an hour .... the plan being that after the religious tapes in the evening had finished I could put on my pre recorded one hour, while I watched Janis Ian on tv, then I would go live at 9pm. After recording the one hour on a cassette I put it in my pocket for safe keeping and so that I would know where it was ..... However as you now know, we played continuous music tapes all evening on the 19th of March as we were doing everything we could to save the Mi Amigo and that cassette stayed in my pocket even as we jumped across onto the Sheerness Lifeboat.
I have copied the tape a few times over the years for people, so I assume that is where the tape has emerged from.
So in short, the tape is genuine and that is the story of how it came into being but was never actually broadcast.
Best wishes,
Nick Richards.