The only real credible certificate would have been an event ticket (with a number and a name) verified by the Waterstones store (that's how one of the fakes was identified).This seller doesn't even have the ticket.
"My experience has been that there are more "ego issues" in autograph collecting than other areas of collecting interest that I have been involved in. " - Eddy
You apparently have never been in a room full of Ocean Liner Memorabilia Dealers. Makes this look tame.