So basically I don't know what got into their heads when they thought this is a good idea, either. At the same time, though, I wouldn't be surprised if this is not an illegal clause per se. If they charge a hundred pounds for structural damage to their hotel, or theft of towels or so, it would make more sense, and if they consider a bad review to be damaging, it isn't even that far fetched. I think they should know better than to do something stupid like this at the end of the day, however.