His failure to declare his links with Amnesty International before ruling on whether General Pinochet was immune from prosecution has led to the unprecedented setting aside of the House of Lords' judgement.

A new hearing will be heard in the New Year, but Lord Hoffmann finds himself very much in the spotlight over the case.

He has tasted controversy before, particularly for his ruling against a journalist who refused to reveal his sources and for his involvement in the Neil Hamilton cash-for-questions case.

The connection

Baron Leonard Hubert Hoffmann of Chedworth, or Lennie to many, has served as unpaid director of the Amnesty International Charity Ltd since 1990.

The charity wing of Amnesty was set up after the organisation failed to win charitable status for its entire operation because many of its activities are political. It pays for research and education work on human rights issues.

Lord Hoffmann's connections with Amnesty don't stop there. His wife Gillian has been an administrative assistant in Amnesty's London office for 21 years.

Responding to allegations of bias, a spokesman for Amnesty said Lord Hoffmann had "no involvement whatsoever in Amnesty International's campaigning work on the Pinochet case".

For his part, Lord Hoffmann has said that standing down from the hearing never entered his mind. "The fact is I'm not biased. I am a lawyer. I do things as a judge. The fact that my wife works as a secretary for Amnesty International is, as far as I am concerned, neither here nor there," he told the Daily Telegraph newspaper.

Indeed, Lord Hoffmann does not have a record of toeing the Amnesty line. As recently as mid-October he made a ruling opposing an Amnesty position while serving on the judicial committee of the Privy Council.

He decided that a convicted killer in the Caribbean, Trevor Fisher, could be legally executed - a sentence which was duly carried out.

An Amnesty spokesman said they were "quite uneasy" about Lord Hoffmann's ruling in the case.

Fast rise to the top

Born into a Jewish family near Cape Town, Lord Hoffmann was the son of a well-known solicitor. He was educated at Cape Town University and then attended Queen's College, Oxford, as a Rhodes scholar. After being called to the Bar, he became one of the most sought after and highly-priced barristers of his generation and was quickly made a judge.

It was as a High Court judge that he has run into Human Rights difficulties before. In November 1989 he controversially ordered freelance journalist Bill Goodwin to reveal the sources of an unpublished article for The Engineer magazine.

Over a period of seven years the case went all the way to the European Court for Human Rights in Strasbourg, where it was eventually thrown out.

Controversial move

At the time of the Neil Hamilton cash-for-questions row he played a part in getting the law on parliamentary privilege changed so that the MP could sue the Guardian for libel. Although eventually cleared to pursue his legal action, Mr Hamilton abandoned it in the day before it was due to begin. He was famously described by the Guardian the next day as a "liar and a cheat".

Lord Hoffmann, who is reckoned by many to be the cleverest of the Law Lords, has has his role in the Hamilton case described as "strangely naive". He is said to hold strong powers of persuasion himself, often winning over other Lords through the strength of his argument.

He was once described by Legal Business magazine as "the most dominant personality in the Lords by a mile".

He is also said to be the most daunting Lord to appear before, revelling as he does in the House of Lords hearings style in which judges fire questions at lawyers.