Tom Griffin of The Green Ribbon has an interesting series titled US Covert Action in Britain Today. He asks if the US is shaping British politics ("public diplomacy") through covert action and largely answers the question through lenses provided by the Roy Godson's Dirty Tricks or Trump Cards: U.S. Covert Action and Counterintelligence. Tom finds it "difficult to believe there isn't an active US Government covert action programme in Britain today."
Well, it may be true. It's also true, if we want to turn this around, that Britain played heavily in American politics prior to and after our entry into World War II. But that was then and this is now.
(BTW: Tom's not done with his mini-series as of this post, having at least "Strategic Aims" to complete.)
I haven't read Godson's book or read any other reviews of it, but from Tom's description, it sounds like he stays in the worlds of black and gray ops (info ops or otherwise). I'm curious if the author considered or know of a comparison between the effectiveness of a white program like the International Visitors Program, documented by a friend as having positively influenced (from the US perspective) Thatcher and Blair long before they ascended to power, to the dark programs alleged / described by Godson.