What was your case again, Andrew?
I'll try a more objective approach. I've changed my mind a couple of times on this, but this is where I've ended up.
We can throw out all the little-guy/$BIGCORP stuff as a fallacious appeal to fairness. The law as written, or as decided in the courts, is under no obligation to treat somebody kindly because the other guy's bigger.
"Slater has been obliged to hire legal help costing thousands of pounds to defend his work, arguing that Wikipedia’s continuing publication harms his livelihood."
His livelihood has certainly to some degree been harmed; but that doesn't mean he has any case.
"The law isn’t hard to understand."
Heh. And coding is easy, and any damn fool can design a bridge. Of the three criteria supplied, Andrew Orlowski doesn't say which he thinks Slater actually meets to a degree which would satisfy a court.
"If he checked the angle of the shot, set up the equipment to produce a picture with specific light and shade effects, set the exposure or used filters or other special settings, light and that everything required is in the shot, and all the monkey contributed was to press the button, then he would seem to have a passable claim..."
Note the conditional If. Slater's quoted as saying - before copyright became an issue - that monkeys stole his camera while he was absent: "He must have taken hundreds of pictures by the time I got my camera back, but not very many were in focus. He obviously hadn't worked that out yet." I think he would have a very hard time arguing that he had creative control over the process, if we believe this earlier version. His later version of events contradicts the earlier, to some degree: adding a description of intent and setting up the camera; which, if we believe it, would give him a stronger case.
"Slater made choices such as choosing the location, the equipment, where it was placed – in front of the monkeys – and choosing what to keep and discard."
Location and equipment would very likely fall under the non-creative "sweat of the brow" element in US law; I don't know what weight UK copyright law would put on it. As to "...where it was placed..." it was moved by the monkey, as we can see from the various photos which have been released, so I can't see that being persuasive. "...choosing what to keep and discard..." is a creative act in forming e.g. an anthology, but I've never heard of that conferring copyright on a single image. If I do an image search and choose a number of public-domain images, I might own copyright to the selection, but for me to gain copyright to a single image by simply choosing it from a selection would be perverse.
"Whether you're on Team Slater or Team Jimbo, it's going to court"
Is it? Do we know that?
I hope he's receiving legal advice along the lines of "Firstly, what will you gain if you win? - a few thousand? It's not worth the risk of pursuing. Secondly, you'll be asked about your various versions of what happened, and how they square with all the photographs obtained. Are you comfortable with that?" Obviously it would make an interesting case for some organisation to take up on his behalf, but I haven't heard that any have done so; which may be telling.
I may well be utterly wrong about all or some of this, which should go without saying; but I don't see that Andrew Orlowski has made any form of actual case in law; as opposed to "$BIGCORP is being selfish!"; which is after all what $BIGCORP has always done.