The Hollow Crown (слэш)

When Asgardian justice stripped Loki of his powers, and exiled him to Midgard, Avengers Headquarters became both his prison and his refuge - until he vanished without a trace. Months later, Natasha discovers a personal message for Tony hidden in a BBC2 television program, and she and Bruce join him on a trans-Atlantic flight. But they don’t know whether they've set off on a rescue mission, or if their special skill sets will be needed to save the Nine Worlds from annihilation.
Cameo appearances by two wizards from the Special Branch of the London Met who assist in aftermath of a battle at a World Heritage site.