Not a pleasure at all. I feel that Ifor gave himself too many liberties. The top and bottom rows were of no help, being unknown. The down clues were, in large part, impenetrable, and it was only through a combination of blind luck and (increasingly fraught) stubbornness that I got anywhere at all.
The identities of the collaborators felt like a final flourish by Ifor: "Oh, how frightfully clever I've been!"