H.P. Lovecraft Holiday Fun Club
This was the rather enigmatic subject of the dedication of an earlier Discworld novel. Research has discovered that this is Pterry's reference to a group of what were then new wave British fantasy and sci-fi authors who seemed to attend just about every conference and fan-meet in the late 1980s and early 1990s.
Members of the happy campers included Neil Gaiman and Mary Gentle (see Reading suggestions). Of course, the association between Terry and Neil eventually created Good Omens.
Mary Gentle's unique take on fantasy fiction is believed to have influenced Thief of Time and was a very definite influence on Unseen Academicals, where Terry made at least one very deliberate homage to her novel of Orcdom, Grunts. (see annotations to Unseen Academicals)