Gary Numan. I believe the year was either 79 or 80. I'd check the details from Strange Fascination but I have no idea where the book is at the moment. I believe David Mallet was somehow involved with the show in question and Bowie used his friendship with the guy as a leverage to kick Numan out. You can't sink much lower than that.

The God you love is gone
He lies broken by your shame
The thing that took his place already died