Why Were IRA Suspects Sent 'Comfort Letters'?

Under the terms of the Good Friday Agreement, people convicted of paramilitary offences were released early from prison.

The scheme did not apply to those who had not been charged or who had been convicted but escaped.

Given that they could not return to the UK, they became known as "on-the-runs".

:: What are "letters of comfort"?

Sinn Fein thought fugitives should be allowed to return without fear of arrest, but the British Government's attempt to devise a formal scheme was opposed by Unionists - and ironically, by Sinn Fein - because the arrangement would have included British soldiers.

The solution was a letter, informing "on-the-runs" they were no longer "wanted".

:: How did the letters come about?

In 2000, Tony Blair asked Gerry Adams to provide names for consideration by the Attorney General, police and Director of Public Prosecution.

In 2002, the Attorney General warned that the scheme could not become an amnesty.

In 2006, Blair wrote secretly to Adams, outlining mechanisms to resolve the issue, "expediting the existing administrative procedures".

:: How did the scheme work?

In 2007, the Police Service of Northern Ireland (PSNI) began reviewing the cases of those wanted in connection with terrorist offences to establish if there were grounds for arrest.

Peter Hain MP, then Northern Ireland Secretary, wanted the scheme kept secret but the PSNI prepared a media statement for use in the event of it becoming public knowledge.

:: How did it become public?

In February 2014, John Downey went on trial, charged with killing four soldiers in the 1982 Hyde Park bombing.

When he produced a letter, stating that he was not wanted by the PSNI or any other police force, the judge ruled that the Donegal man could not be prosecuted.

The letter had been issued in error.

:: How many letters were issued?

Of the 288 names submitted for consideration, 156 people received a "letter of comfort" and 31 were informed in some other way that they were not wanted for questioning.

Drew Harris, now Deputy Chief Constable of the PSNI, told the Northern Ireland Affairs Committee that 100 of the recipients are suspects in 300 murder cases.

:: What did the government inquiry find?

When NI First Minister, Peter Robinson, threatened to resign over the issue, David Cameron announced an inquiry.

Lady Justice Hallet concluded that the letters were not an amnesty and the scheme had been lawful.

But she found "significant systemic failures" in how it operated and branded Mr Downey's letter a "catastrophic mistake" by the PSNI.

:: What did the Northern Ireland Affairs Committee find?

The Committee, which established its own inquiry because it felt the government's was too narrow in remit and too private, concluded that the scheme was "questionably unlawful" and "distorted the process of justice".

Members called on the government to take all necessary steps, including legislation if necessary, to ensure the "comfort letters" have no legal effect.