Some of us older enough may remember a late night programme called Cue The Music on ITV which was presented by a certain Mike Mansfield.
You'd tune in basically to watch an old live performance of Hawkwind or something with an intro from Mansfield sitting at a mixing desk.
Slattery would often appear (it was an-joke) as one of the staff on the mixing desk at the start making odd faces. I clearly remember a bizarre episode when he's walking about in the background in a gimp suit.
Unless you knew the in-joke and were just settling down for Hawkwind after a few beers you'd have missed him.