Fosse76 said: "if the book goes unsold they will not be able to return it to the publisher. And while many bookshop owners no doubt would love to mark-up and feature the autographed copy, there is a saturation point and they may not be able to sell the signed copy."
Once this is posted on the Internet, anyone near the National Theater will be checking all the nearby bookstores for this. I don't think you need to be concerned about it being remaindered, especially in the first week of Hamilton playing the West End, heh.