A team of detectives is due to re-open files on 100 unresolved murders of the Northern Ireland Troubles.
Dave Cox and Phillip James of the HET
It marks the official start of work by the Historical Enquiries Team, which has a budget of more than £30m.
The team, led by retired Metropolitan Police Commander David Cox, will re-examine a total of 3,268 killings between 1969 and the 1998 peace accord.
They will begin by focusing on murders from April 1969. The entire review will take up to seven years to complete.
The Historical Enquiries Team has a two-fold role: to assist families with any unanswered questions, and to ensure that all remaining investigative opportunities are examined and exploited fully.
The squad of about 100 detectives and support staff will use the latest forensic science and intelligence analysing technology.
Northern Ireland's Chief Constable, Sir Hugh Orde, said he hoped it would bring closure to many families.
Mr Cox said the team's two main aims would be to "offer answers and a greater level of resolution to bereaved families".
There will be two distinct investigative units - one will be made up exclusively from officers from outside Northern Ireland, who would work on cases, where, for example, there had been allegations of security force collusion.
The team said they would be operationally independent from the PSNI, but would report to the chief constable.
The Northern Ireland Secretary, Peter Hain, said it was quite possible that people would serve jail terms as a result of the new murder investigations.
He said some of the murders involved members of the security forces and all would be investigated thoroughly.
The team will need between five and seven years to complete its work.