It's maybe one of the 3 best drama series of the last 20 years, and easily one of the 5 best. For a (nonfic) book in the same vein, try The Billion Dollar Spy.
I really liked The Americans, too.
Right down to the local ambassador (I think it was) who wanted to stop the operation but it was escalated all the way to Thatcher who was at Balmoral at the time and who was outraged at the idea that the UK wouldn't try and rescue him.
Whether Gordievsky was a triple agent or not, it's clear that the KGB desperately needed a conduit to convey useful (true) information to the West in a form that Western intelligence agencies would find credible. Western intelligence (particularly the UK) also desperately needed an asset who could produce that sort of intelligence. Gordievsky just happened to be a perfect conduit for this communication, and may have helped avert a truly stupid nuclear war.
If you assume this was an "op" then it would have to end somehow. Ideally it would end in a way that left Gordievsky alive and in the West, where he could continue to deliver his message to politicians. In order to keep Gordievsky's past information credible, he would either need to (1) be caught and tried/imprisoned, (2) defect. But I would imagine that the best case for his credibility would be some amazing combination of (1) and (2), especially a situation that would force the West to commit resources to a heroic escape that took him right out from under the KGB's nose in Moscow. This would make his handlers look brilliant, and it would make Gordievsky the kind of hero that politicians would take seriously. It would also be politically almost impossible for anyone in US/UK intelligence to ever (publicly) voice skepticism about Gordievsky.
Gordievsky's escape from Russia also seems extremely bizarre. Remember this is a man who has miraculously survived chemical interrogation, is liable to be shot at any moment, but has somehow slipped his KGB tail and traveled halfway across Russia to a border town. Whatever doubts the KGB had before, he is now a dead man if they catch him. Yet instead of hiding in the woods waiting for his rescue, he heads into town, gets drunk, falls asleep in a restaurant and nearly misses the appointment to escape to the West? I guess people behave strangely under stress, but there's strange and there's "death wish." Perfectly reasonable, though, if the whole thing was fake.
Finally there's the fact that Gordievsky's arrest story was almost immediately verified by Vitaly Yurchenko, whose "defection" is utterly bizarre. Yurchenko just happened to be an expert in "special drugs" who defected right after Gordievsky escaped, basically for the sole purpose of solidifying Gordievsky's story and drawing attention away from Aldrich Ames. Then, literally weeks after delivering his confirmation to US intelligence, Yurchenko walks out of a Washington, DC restaurant and heads straight back to the USSR where he is awarded the Order of the Red Star for "a successful infiltration operation."
What is the theory of the case here? I'm not following what this KGB need/matching British intelligence need was and how it was met through Gordievsky's defection.
MI6 suffered a string of defections to the USSR in the 50s and 60s, which hurt the organization and put it in a "defensive crouch." Since intelligence production was very important to the US/UK relationship, this put MI6 in a position where it would be relatively eager to accept the bonafides of a new UK-based KGB "double agent" that dropped into their lap. And so dropping one into their lap in the 1970s would make plenty of sense.
But this does not mean anyone had a real plan on how to use Gordievsky at the time. And in fact, he's immediately recalled back to Moscow on some pretext.
In the 1980s, Andropov begins running around looking for a pretext to launch a nuclear war. He can't do this as KGB chief, but he's doing everything he can to assemble the evidence for it. And the writing is on the wall by 1981: soon Andropov will become to General Secretary, where he will have the authority to launch missiles. Somebody needs to defuse this situation, but you can't tell Andropov he's insane and there's no official channel to warn the West.
Coincidentally, and about four months before Andropov becomes General Secretary, Gordievsky re-appears. But now he's been turned into an irresistible dream asset, maybe the best human intelligence asset the UK could ask for: a high-ranking intelligence officer at the KGB station in London, clearly on his way to running the place. He should be able to produce all kinds of information that would immediately shut down all kinds of operation.
Except curiously, Gordievsky produces almost no really valuable information that would hurt the USSR. The intelligence he carries with him is described as a "trove", but on closer inspection, this stuff is juicy but utterly worthless: just a bunch of aging lefty political figures who aren't producing useful intelligence for the KGB and probably never did. But surely Gordievsky will expose dozens of London-based KGB spy networks? Except weirdly he doesn't do that, either; conveniently the main "intelligence" finding he delivers is that there are no KGB spy networks in London, so there is nobody to burn.
In fact, almost the only real piece of intelligence Gordievsky ever offers is the fact that Andropov is panicking and trying to assemble the case for a pre-emptive strike. He delivers this information instantly, and then delivers it again and again. When Able Archer happens, he rings the alarm even louder. This doesn't compromise the KGB one bit: in fact the result is entirely advantageous to the USSR, since it convinces Western militaries to back off.
He then gets promoted to an even more important position, where he basically becomes a political go-between transmitting information from the Russian leadership to the West. At one point he's basically writing Gorbachev's speeches, while convincing the West that Gorbachev is legitimate. The result is also not harmful to the USSR: indeed, it ensures that Gorbachev's visit is a resounding success.
My point here is that if the USSR wanted to deliver a high-level agent that could provide "useful" information (from the perspective of the USSR) while doing minimal damage to the USSR itself, they would have had a hard time doing better than Gordievsky. And it makes plenty of sense to exploit the UK's desire to be the conduit for such information, rather than sending Gordievsky to Washington where he would be one source among many.
In the 1980s, Andropov begins running around looking for a pretext to launch a nuclear war.
is at odds with everything we know about Soviet doctrine and intent, both from the period itself and the voluminous info that's come out subsequently. The bar to hang a serious (or even plausibly fictional) theory on this is very, very high. I'm not suggesting you did, of course - you qualified it as 'spitballing and counterfactuals'. But it's a really long spitball, to my mind at least!
Edit: if you happen to speak Russian a recent interview with Soldatov/Borogan covers some of the interesting differences between outward projection and insider culture regarding defections in the Soviet security services.
https://meduza.io/episodes/2023/08/17/kak-ustroena-rossiyska...
1. The Wire
2. Breaking Bad
3. DarK (German)
4. Halt and Catch Fire
5. Bosch
Others- True Detective S01, S03, Westworld S01, Generation War (German), Happy Valley, Mindhunter, Mad Men, Silicon Valley, The Sopranos, The Fall, Band of Brothers, Rick and Morty, Veep, Babylon Berlin (German), Arrested Developtment, The Americans, Narcos (Spanish), Fauda (Hebrew-Arabic), Black Mirror, Bojack Horseman, Vinland Saga (Japanese, Anime), Fargo S01, S03, Kleo (German), Freaks and Geeks, The Marvelous Mrs. Maisel, Mozart in the Jungle, Tales from the Loop, Panchayat (Hindi), Paatal Lok (Hindi), Broadchurch, Yellowstone, Tales from the Loop, and Charite (German).