An operation looking into the involvement of an alleged British state agent known as Stakeknife in murder, kidnap and torture has cost over £37m since it was launched.
Operation Kenova is the independent investigation being led by former Bedfordshire chief constable Jon Boutcher into a range of activities by an alleged individual.
West Belfast man Freddie Scappaticci was alleged to have been the Army's top mole in the Provisional IRA, but had denied this until his death at 70 years old this year.