Two separate investigations into human rights abuses, headed by Spanish High Court judges, have implicated the former Chilean military leader, Augusto Pinochet.

General Pinochet: Now 82 years old, he has always maintained he acted for the good of Chile

One is specifically into the extrajudicial killings of Spaniards, or the disappearance of Spaniards in Chile in the years after General Pinochet took power in 1973.

The other concentrates on Argentina, but is also looking into Operation Condor, during which the secret police services which served the military dictatorships in Chile, Argentina, Brazil, Uruguay and Paraguay, exchanged information and prisoners. Gen Pinochet, it is alleged, was one of the main organisers of the operation and his secret police reported directly to him.

Slow progress

Relatives of the Spanish victims, often working closely with relatives of victims in Chile and Argentina, started their cases against Gen Pinochet and against several members of the Argentinian military regime about two years ago when they felt the investigations in South America were not making sufficient progress.

But progress in the Spanish investigations was always going to be slow.

The alleged crimes were committed several thousand kilometres away and more than 20 years ago. There are few surviving witnesses willing to talk.

The main stumbling block, however, has been the lack of political will to deal with the issue among Spain's European partners.

General Pinochet has visited Britain several times over the past few years and every time human rights organisations, such as Amnesty International, have urged the authorities in London to arrest him.

Amnesty says that under the terms of the United Nations Convention against Torture, any state is obliged to take into custody or take other legal measures against anyone who is alleged to have committed or been party to torture.

The British authorities have always said they had no right to detain Gen Pinochet while he was visiting in his capacity as a private Chilean citizen. Gen Pinochet has always said that as a Chilean senator he has diplomatic immunity.

Cooperation on terrorism

But on this occasion, the Spanish authorities made their request, through Interpol, under the terms of the European Convention which requires signatories to help each other on matters relating to terrorism.

Families of the Spanish victims wrote to the British government urging it to act in accordance with commitments it made when it came to power to promote international human rights. The Spanish investigations have made little progress in recent months and needed some kind of significant breakthrough.

The request to question Gen Pinochet was probably made more in hope than expectation - although the British and Spanish authorities have been working increasingly closely in recent months - most notably over the arrest in Spain in August of Kenneth Noye, wanted in connection with a murder inquiry in Britain.

Whether Gen Pinochet ever stands trial seems unlikely. He is 82 years old and in poor health.

He is also unlikely to answer many of the questions asked of him. He has always maintained that whatever he did was necessary for the future wellbeing of Chile.