This was an interesting and spectacular performance, and I don't know is Sotheby's was "in it", but I think it would be good to clear some misconceptions and propose a view on "how did he do it", as the method behind this demonstration uses some principles of deception that have been used in similar form in magic.
A few people asked themselves whether a battery hidden in the frame in 2006 could have worked in 2018. Of course it could, but why risking it? The battery was replaced before the auction. If you check the various press releases,
auction catalogue and stories, you will see that the picture was authenticated by "
PestControl", the only company able to authenticate Bansky's work. As PestControl is closely associated to Bansky, it is the first suspect for somebody that could have replaced the batteries. To check and validate the picture, it will have had to be removed from the frame, checked under a microscope/special lights, etc. The checking of the picture was pure misdirection (but it was necessary to legitimately authenticate it), and would have been the perfect reason to change the batteries. This stratagem has been used in magic for centuries: Houdini himself had a "committee" to check his cabinet, and quite often a member of the committee would have left inside the necessary tools to affect the escape. Some other times, when magicians have committees to check apparatus, somebody there is used to activate the trick.
All the paintings in the sale were displayed hanging: the
sale only had 40 paintingsand these were hanging around the room in Sotheby's gallery. The Bansky one was not the only one hanging: I don't where the NYT has got its information.
There are a couple of things that cast a doubt on Sotheby's being "in it" and these are the strong relevance given to the frame in the auction catalogue. In the description, you find: mounted on board,
in artist's frame and in the long description:
Bordered by an ornate gilded frame, an integral element of the artwork chosen by Banksy himself. If it can be proven that Sotheby's was in it (which is difficult, as the text could have been written by somebody following a press release from the artist), this could be the classical give-away that plagues inexperienced magicians when they say:
I have here an ordinary, unprepared deck of cards. We (should) learn to guide the attention of the audience to some elements, while leaving others in the shadow... it doesn't seem to have been the case here.
About the Bansky being the last item in the sale, this just makes sense, as Bansky was probably the best-known name (outside the art world) and, as in every good show, the "star" comes on at the end. Also, while this picture sold for relatively little money, compared to other pictures in the same sale and in the one immediately before, this specific image is very well known, so it would have made sense to keep it for last. And this is another item that raises the suspicion of Sotheby's being "in it".
I think this was a nice magic trick that has gone viral: well done to all parties involved for creating something memorable using our techniques!