I recently watched the Sherlock TV series again. One thing is bugging me: how could Eurus Holmes tell Mycroft about the upcoming terrorist attack in London? I mean, according to Mycroft, Eurus had no contact with outside world (until she met Moriarty) so she would have had no idea what events were occurring.
Eurus recruited those sent in to her presence, allowing her more and more control at Sherrinford
Although Eurus was notionally in solitary confinement at Sherrinford, the governor did not keep sufficiently close control over who was allowed contact with her.
MYCROFT: Has there ever been, against my express instructions, any attempt at a psychiatric evaluation of Eurus Holmes?
Eurus then used her manipulative gifts to 'recruit' them to serve her agenda rather than the facility.
GOVERNOR: Everyone we sent in there ... it's hard to describe, it's like she...
HOLMES: Recruited them?
GOVERNOR: Enslaved them.
HOLMES: She's been capable of that since she was five, she's an adult now!
As she gradually asserted increasing control at Sherrinford, Eurus would have gained access to news of the outside world, and any contacts from the world of crime.