MI5 assets and informants

Somewhat similar, perhaps, to FBI or CIA in United States, but only in a certain crossword puzzle fashion

U.K. High Court slams MI5 over informant deception and lack of transparency

MI5 false evidence was a serious failing, Cooper says
The home secretary says the government accepts the high court’s ruling that an independent investigation should take place.
The two reviews took place after the BBC revealed MI5 had lied to three courts in a case concerning a neo-Nazi state agent who abused women. The flawed reviews cleared MI5 of deliberate wrongdoing.

This gets stranger and stranger.

One of the features of the abuse in that relationship was that this man, X, boasted to her that he was an MI5 informant, or that he was working for security services in the UK ...

Neither a feature of abuse nor a boast, as apparently a senior MI5 official admitted Beth's "X" was working for them. Nor is "X" possibly abusing his authority in court, none of his own to speak of.

Bizarre divorce cases are reaching very high courts in Europe.

"Neo-Nazi state agents who abuse women" certainly do exist in Britain as well as America, Canada, continental Europe and Russia, but the particulars of this case have not been made clear at all to the general public.