It is amazing to learn how much the East German intelligence agency Stasi spied on and influenced British politics. The Stasi was a kind of branch office for the KGB, a placeholder for Moscow (like Ukrainian operators would seem to be a placeholder for Moscow today), and, according to Anthony Glees, the top British expert on the subject, "Britain and especially London were riddled with Stasi spies of one kind or another." 

Glees' quotation is from his 2003 book, The Stasi Files: East Germany's Secret Operations Against Britain, which focuses on the decade spanning 1979 to 1989, the year that East Germany dissolved itself. For ten years, from 1992 to 2002, scholars like Glees were able to study such nefarious matters inside the the Stasi archive, which, for that golden-opportunity-decade, was "the only security and intelligence service archive in the world ... open to scholars." 

These documents of treachery and subversion may have other repositories, not least being the CIA. 

According to Glees, sometime in 1989, the CIA was able to buy for $1 million a large cache of Stasi files which included the cover or code names of the British Stasi agents and their real, or "clear" names.

He writes:

As is discussed below, it seems probable that the only complete record of the true identities of the Stasi's Western spies is now held by the CIA, which may or may not choose to make it public at some times in the future. Sources close to the CIA insist that the names will never be made public because there is an "operational aspect"  to possessing them. What this means is that the CIA may see some use in the people concerned. perhaps as double agents, in the future. (Emphasis added.)

This is something to bear in mind as we try to understand British involvement in the anti-Trump conspiracy.