What are we to make of the release of the man convicted of the Lockerbie plane bombing which took the lives of 270 people, some of them on the ground in that small Scottish town, the night people literally fell out of the sky, some still strapped into their aircraft seats?

Was Ali al-Megrahi, who is said to be dying from terminal, aggressive prostate cancer, the man who planted the bomb on that Pan Am aeroplane coming up to Christmas 21 years? It seems that you pay your money and take your chance on that one.

The Scottish legal system found him guilty. The Director of the FBI, Robert Mueller, is equally convinced. Indeed, such is his fury at the release of al-Megrahi, that he wrote a letter to the man who set him free, Scottish justice minister, Kenny MacAskill, in such vitriolic terms it is a wonder it did not spontaneously burst into flames when exposed to the open air.

There can seldom have been such a missive sent from the security services of one country to a its friendliest and longest standing ally. He described the decision to release al-Meghrahi as making a “mockery of the rule of law”.

Mr Mueller, like all those heart-broken relatives like Dr Jim Swire, whose daughter was on the plane, believes the Libyan is guilty.

And there is a belief that his release was part of a wider diplomatic game — shamefully involving improved trade links with Libya — which had little to do with justice and everything to do with politics.

The conspiracy theorists are having a field day. Was the bombing of the Pan Am flight really a revenge attack by Iran or its agents for the shooting down of one of its airlines by the Americans some time earlier? That was recognised as a tragic error, but no-one was ever brought to account for it. Whatever the reason the passengers on the Iranian flight were just as innocent — and just as dead — as those who plunged to earth over Scotland.

The theory runs that it was easier, 21 years ago, to blame Libya than Iran for Lockerbie again for political reasons. Libya, with its known terror links to the IRA, was a likely, and convenient, scapegoat.

The oft repeated comment by Lord Denning, Master of the Rolls, in rejecting an action being brought by the Birmingham Six against West Midland police in 1977 comes to mind at this time.

He said: “If they won, it would mean that the police were guilty of perjury; that they were guilty of violence and threats; that the confessions were involuntary and improperly admitted in evidence; and that the convictions were erroneous.

“That would mean that the Home Secretary would have either to recommend that they be pardoned or to remit the case to the Court of Appeal. That was such an appalling vista that every sensible person would say, ‘It cannot be right that these actions should go any further’.”

The Birmingham Six, of course, were later freed and pardoned. It is widely accepted that they did not commit the IRA bombing of two pubs in the city killing 21 people. The real bombers made it back to the Irish Republic and six men spent years in jail for a crime they did not commit — but which Lord Denning could not contemplate they were innocent of.

Justice is a very inexact process, irrespective of what many people will argue. It would be comforting to think that the courts never convict innocent men or that innocent people are not put in the dock. It would be comforting, but it would be mistaken to so believe.

We know that many people in Northern Ireland languished in jail because of wrongful convictions and, equally disturbingly, many guilty people escaped any punishment at all.

Mr Mueller, in his letter to Mr MacAskill, said: “You have given those who sought to assure that the persons responsible would be held accountable the back of your hand.”