I found this a good read (though it is all secondary sources). But the author’s recommendations are rather restrained (presumably in line with the HJS’s principles), i.e. a public enquiry and legislation to force transparency or to block certain funding. But even if those were to happen (and there’s no such sign: the government is currently sitting on a pertinent 2016 report by the Home Office’s Extremism Analysis Unit) it would be s l o w indeed and there would be ways out, legal and otherwise. But here’s the thing (and just to extend what HM said): if it’s so bloody obvious that Saudi Arabia is financing Wahhabist Islam in the UK (and everywhere else for that matter: some $2 to $3 billion annually since 1975 apparently) and that this is the breeding ground of ‘home-grown’ Islamist terror, then the government’s apparent lack of action against the Saudis implies that it sees a terrorist fallout for us as a fair trade-off for ‘maintaining close ties’. If that’s true, we are f****d.
(The Yemeni government may be ‘internationally recognised’, but the Saudi reasons for bombing the Houthis (largely Shia) are not unconnected to the fact that the Yemeni majority is Sunni, the source of the Wahhabist ideology the Saudis are spreading around the world.)