After the collapse of the trial of Chris Ward the Police Service of Northern Ireland yet again comes under critical scrutiny for its handling of a high-profile investigation.

Sir Hugh Orde, its chief constable, has presided over three of the UK’s most controversial cases — the 1998 Omagh bombing, the Northern Bank robbery and the murder of Robert McCartney — at the end of which he has scored a legal 0-3, at home, with not a single conviction achieved.

A harder question to answer is how much blame for this dismal record should be shouldered by Sir Hugh — a frontrunner for the post of chief of the Metropolitan Police — and how much is the result of the peculiarities created by the peace process and the blurred point at which justice and politics meet in Northern Ireland.

Even now the province’s new and lavish political structures are paralysed because of a dispute over the devolution of justice and police powers from Westminster to Stormont.

Other investigations that have not yet yielded any charges include the shooting dead of the British agent and senior Sinn Fein member Denis Donaldson and the beating to death of Paul Quinn, who had almost every bone in his body smashed by his attackers, whom his family swear are IRA men.

Although both men were killed on the Republic’s side of the border, the PSNI has a primary role as the murder suspects are believed to be from Northern Ireland.

Sir Hugh was not in charge when the Real IRA bombed Omagh in the worst single terrorist atrocity of the Troubles with a death tally of 29 and unborn baby twins.

But it was his officers who brought Sean Hoey to court in the largest murder trial in British legal history. Mr Hoey was acquitted amid scathing criticism of the PSNI from the judge.

Sir Hugh replaced Sir Ronnie Flanagan in 2002 after the Royal Ulster Constabulary was rebadged as the PSNI as part of the peace process. He was at the helm for the Northern Bank raid investigation in Belfast in December 2004, which at the time was the largest cash robbery (£26.5 million) in UK history.

Almost three weeks after the Northern Bank raid he told a news conference in Belfast: "In my opinion the Provisional IRA were responsible for this crime and all main lines of inquiry currently undertaken are in that direction."

The charge was denied by the Provisional IRA and Sinn Fein, its political wing, said that it believed the group. By the time Sir Hugh made his public pronouncement senior London and Dublin politicians had long been in agreement that it was the work of the IRA.

His delay in publicly attributing blame — in a province where the police were traditionally more swift to point the finger of blame at the activities of paramilitaries — may have been because of the febrile political atmosphere of the time.

Days before the robbery No 10 was briefing Westminster political reporters that Ian Paisley’s Democratic Unionists were about to do a power-sharing deal with Sinn Fein. Tony Blair’s spin-doctors were 18 months premature, but they were right in the end.

The Northern Bank raid, followed swiftly by the murder of Robert McCartney by a republican mob in a pub brawl, threatened to unravel all the patient, mind-numbing choreography that led from the 1998 Good Friday Agreement to the restoration of Stormont.

In June this year Terence Davison, the only person to be charged with the murder of Mr McCartney, was acquitted. His sisters, whose campaign for justice took them to the White House, again accused Sinn Fein and the IRA of obstructing efforts to bring their brother’s killers to justice.

Significantly the chief constable, in accusing the IRA of the Northern Bank robbery, said that he had not bowed to any pressure to attribute blame but was doing so now because it made "operational sense".

Right on cue, proving the chief constable’s instincts right, Martin McGuinness, now the Deputy First Minister, accused Sir Hugh of making “nothing more than politically biased allegations”.

But the Taoiseach Bertie Ahern gave a glimpse of the anger in Dublin and London when he suggested that the bank raid would have had to have been approved by the IRA’s army council and therefore was without doubt known in advance to Sinn Fein’s most senior leaders.

"An operation of this magnitude ... has obviously been planned at a stage when I was in negotiations with those that would know the leadership of the Provisional movement," he said.

Michael McDowell, the republic’s justice minister, went further: “The Provisional movement is a colossal criminal machine laundering huge sums of money. Their mask has now slipped. Their balaclavas have come off.”

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