Re M the GM comment "I remember starting a review with the words "We will miss Steeleye Span" when they broke up in about 1976 or so. Peter Knight was missing from their lineup for years after Bob Johnson & Rick Kemp joined".
Peter was only missing from the lineup during the John Kirkpatrick/Martin Carthy era which spanned 1977 to 1979. I think that you will find that he has been present in every other line-up before and since (except the first, short-lived Hark the Village Wait line-up.