[And now, his voice is very, very calm. There is no anger.]

Vigilantism is the only way anything will be done against him. Here or in London.

He won't give you lot another chance to arrest him. He won't let Mycroft get hold of him again. He won't leave any more evidence than he already has.

The only way he can be stopped is by a vigilante. Someone unconnected with the police. Someone just as untraceable. [Someone who is recorded as dead. Because you can't try a dead man for murder.]