It is since 2006. To clarify, the U.K. has succeeded in revoking citizenship, but in all of those cases the end result of that process is to keep people out of the U.K. or to deport them, not to bring them to justice.
Again, to come back to your first point, I think a concern that's shared by everybody in this room is that people who perpetrate heinous acts should be brought to justice and prosecuted to the full extent of the law, not sent away to some quiet corner of the world where they can plot against you.