Earlier quoted context omitted.
You are over-stating the significance of the SWP. Maybe what you say is true of the 80s, but it isn't today. They are not the main party to the left of Labour, the greens are. The greens have 50,000 members and received 850,000 votes in the 2019 election, the SWP has a few thousand members and does not even field candidates. In my experience they have little influence on the Labour grassroots. The SWP's standing amon…
Given your username, I'm curious. Are there many left anarchist activists in the UK at the moment? I had some tenuous contact with the ACF in the late-90s, but it doesn't seem a very active or impactful part of the political landscape.
There was a very concerted and covert anti-left push during the 80s and 90s. Anti-establishment groups of all kinds - anti-nuclear protesters, greens, animal rights activists, and official far left groups like the SWP - were infiltrated by undercover police and sometimes subverted.
It's an ongoing scandal, although it's been lost in the noise from other events over the last year or two. Undercover police with fake identities had relationships with activists and sometimes fathered children with them.
In some cases they worked internationally and were responsible for criminal acts (i.e. terrorism) which discredited the organisations and movements they infiltrated.
https://en.wikipedia.org/wiki/UK_undercover_policing_relatio...
It's hard not to suspect the apologies are disingenuous. The plan was to subvert, marginalise, and discredit left wing views, and to destroy left wing organisations of all kinds.
And it seems to have been very successful.