Had I been able to erect a fence across the pier at Mountshannon recently, I might have made money by charging a fee to the many folk who walked down to look at the Shannon Princess II. When I told one chap that it was a hotel barge, he asked if he could go there for lunch. I tried to explain, but this notice from TravelWorld may explain it better.
Admittedly the headline is a bit misleading: when I saw it first I thought that the guests were to dress as artisans, whereas in fact the theme is artisan food, which means food made by members of the middle classes for sale to other members thereof. Put it this way: you might not invite the staff of your local Aldi to your garden parties but you would be quite happy to have your artisan food suppliers there. Not that I’ve anything against “artisan” food per se (indeed I buy lots of it); I just dislike the name.