Northern Ireland - police knew of agent's murder in advance

Belfasttelegraph: Senior cops knew of a plot by a notorious Army spy to kill one of their own agents - nine months before the murder.

The shock revelation is contained in secret security files, which also show that two Special Branch officers weren't told of an IRA plot to kill them.

The leaked documents - described as "devastating" by a senior security source - also indicate that an IRA informer was sacrificed to protect a more highly regarded informer. Link

Further 'detail' at cryptome