I've seen the Brocock cartridge compressed airguns.Skennerton isn't in the business of stopping people from taking wooden nickels, so I think the real reason he won't commit himself without personal examination is the large number of far better done No.4T fakes (etc. etc.) which come on the market.
Saxby and Farmer are almost certain to be the British Saxby and Palmer. Here we have a minor difficulty, for there is no telling how long some of these minor British firms have been in business, or what they made when gun laws allowed for a bigger market. But in modern times they made airguns. Their commonest were German zinc alloy framed but real revolvers, I think Weihrauch, adapted to fire only their own very ingenious and efficient compressed-air cartridges. But they also did similarly fuelled conversions of real rifles, mostly Lee-Enfields. They were banned some years ago, and in contrast to cartridge handguns, they became unownable under any circumstances, and without compensation. To be fair, controlling airguns had nothing to do with it. The revolvers WERE being converted to cartridge use (probably very inefficient and dangerous use) by mostly West Indian drug gangs.
It's even possible that this rifle was once a Saxby and Palmer airgun conversion, and/or had "Saxby and Palmer" stamped on it. I suppose some people would count nine letters right out of eleven as more than 90% right. Or maybe he just needed to think of a name.
A airgun built on a real Enfield might explain the radically tilted scope. low velocity yet some get pretty good accuracy at longer ranges than you might think, especially those that can handle a heavy pellet.
The Brocock cartridges were sometimes bored out to take a 8mm theatrical blank and a bullet heavier than the pellets it was made for. Velocity was said to be lethal.
The guns also might be movie props.
A friend had to lower the front mount of a one thousand yard target rifle years ago to get enough elevation, not that radically though.
From the position of the lever the mount may not be fully engaged in those photos.