The highest court in Britain will announce its ruling today 1400 GMT on whether the former Chilean dictator, Augusto Pinochet, is immune from arrest and extradition.

The general was arrested in London last month while undergoing medical treatment.

Five senior judges are to decide whether to uphold a High Court decision that he is immune from prosecution because the crimes he's accused of were committed when he was head of state.

A ruling in General Pinochet's favour means he would be free to return to Chile.

But if the verdict goes the other way, he could face extradition to Spain on charges of genocide, terrorism and torture.

The judges, who are reported to be divided on the issue, have themselves described the case as very difficult.

Chilean exiles have been holding an overnight vigil in London in advance of today's courtdecision.