Apologies not always enough to right wrongs of past
Alan Turing is sometimes described as the greatest British mathematician of the 20th century and the father of the computer era, whose outstanding skill at code-breaking probably shortened the Second World War by two years.
But he was convicted of homosexual offences in 1952 and, two years later, died by cyanide poisoning.
Now there is a growing campaign, led by Stephen Hawking and other scientists, to have Turing officially pardoned for his 'crime'.
Turing was originally sentenced to prison, but accepted 'chemical castration' - a series of oestrogen injections - instead. His suicide, at the age of 42, robbed science and mathematics of a brilliant brain. The tragedy of Alan Turing is rightly regarded today as a matter of shame and regret.
In 2009, the then prime minister, Gordon Brown, apologised for the unjust penalties Turing had undergone. Now the campaign for a retrospective pardon is a step further in rehabilitating a great man.
Yet not everyone favours Professor Hawking's crusade for a pardon. Some believe it isn't honest to try to change the past. If Alan Turing is to be 'pardoned', why not every gay man who lived, then?
Apologising for errors and mistakes of history, or perhaps just revisions of attitudes, has become a regular public practice.
Sometimes, these apologies are useful and help to encourage attitudes of reconciliation. Sometimes, such gestures are regarded cynically.
Tony Blair famously apologised for the Irish Famine of 1845-50 and, while his words probably had a positive effect on Anglo-Irish relations, they were regarded with a certain cynicism in political circles.
David Cameron's apology for Bloody Sunday was, in a way, more plausible, as the event took place within living memory and involved still-extant agents of British political power.
The apology for Bloody Sunday also helped the work of peace and reconciliation in the north, although there are some people who called for London to actively prosecute all serving soldiers involved at the time.
By the same token, the Republic's defence minister, Alan Shatter's pardon last June of 4,500 Irishmen who deserted the national army to fight for the Crown (and the Allies) in the Second World War represented a significant change in attitudes.
These men had been harshly treated on their return home, blacklisted and stigmatised and many spent the rest of their lives marginalised and in poverty.
The soldiers' pardon almost seeks to delete a historical truth - that the majority of the Irish nation were affirmatively neutral during the Second World War.
Perhaps apologies and pardons are a question of time and perspective and also, perhaps, a question of usefulness.
Maybe a more constructive way of honouring Alan Turing would be to place his statue on the fourth plinth in Trafalgar Square, elevating him for his genius, rather than singling him out for his sexual orientation.