Supposedly an adolescent favourite of Lewis himself (Kevin Whately), who has some of their albums, their manager claims they were the third biggest-selling progressive rock act of all time. Their signature song (which we never get to hear) was "Counter Culture Blues", apparently "the anthem of a generation". Among the intrigue is that the bassist apparently wrote the song but was so out of his head on Mandrax that he didn't even remember doing it and gave the publishing away to the lead guitarist as a result, and the mysterious "return from the dead" of lead singer Esme Ford (played by Joanna Lumley with an Irish accent that she can't quite manage to keep up for an entire sentence), whom everyone believed had thrown herself into the sea many years earlier.
In fact, Esme Ford did throw herself into the sea, and the one who "returns" is an imposter. The episode's murder victims are the people who had figured this out.