John Downey’s collapsed trial for the Hyde Park bomb murders triggered a major political controversy over the until then little known On the Run scheme.
The OTR scheme was set up by Tony Blair’s Labour government in 2000 in response to Sinn Fein lobbying for republicans who had fled the UK during the Troubles and were unsure whether they were wanted by the police.
The republican party had stressed the importance of addressing the issue in the context of shoring-up republican support for the peace process.
Under the terms of the scheme names of individuals were passed to the Government, the majority through Sinn Fein.
The names were then handed to police and prosecutors to assess their status.
A report on each individual, some of whom were Sinn Fein members, was sent back to the Government and, if they were declared as not being wanted, a letter of assurance was then issued to the individuals.
In February 2014, Old Bailey trial judge Mr Justice Sweeney found that Mr Downey’s arrest at Gatwick Airport in 2013, when he had been sent a letter in 2007 stating he was free to return to the UK, represented an abuse of process – not that the letter conferred immunity from prosecution.
Mr Downey, 66, has always denied involvement in the 1982 Hyde Park bomb attack by the IRA.
The PSNI was heavily criticised in the wake of the judgment as an evidence report it compiled on Mr Downey, which the Government used to determine whether to issue the letter, had not stated he was being sought by the Metropolitan Police.
A judge-led review of the OTR scheme ordered by then prime minister David Cameron found that it was systematically flawed in operation, but not unlawful in principle.
Lady Justice Hallett said a “catastrophic” error had been made in the Downey case, but she insisted the letters of assurance did not amount to amnesties or get-out-of-jail-free cards.
Following the probe, the PSNI undertook to review the evidence in all 228 applicants made under the scheme to explore whether other errors have been made.
That exercise is still ongoing.