Lord Slynn of Hadley was a distinguished lawyer who made significant contributions to the development of administrative, employment and European law. He served as Advocate General and then as a judge at the European Court of Justice before completing his career in the House of Lords.

Gordon Slynn was born in 1930 and attended Sandbach School in Cheshire, Goldsmiths’ College, London, and Trinity College, Cambridge, where he was a senior scholar and subsequently sub-lector. Called to the Bar by Gray’s Inn in 1956, he became a member of chambers at 1 Hare Court in the Temple and began to specialise in commercial work.

However, his abilities soon came to the attention of the Crown. In 1967 he was appointed Junior Counsel to the Ministry of Labour. Appearing in complex tax cases in the Divisional Court, he made his points with calm, unaggressive force and enjoyed success in several seemingly unwinnable actions.

One year later he became Junior Counsel to the Treasury, or “Treasury devil”. In this capacity, Slynn served three attorney-generals — Elwyn Jones, Peter Rawlinson and Sam Silkin. Each, in turn, came to depend on Slynn’s qualities: his astute legal brain, his skill as a draughtsman, his flair as an advocate and — above all — his excellent judgment. In his autobiography, A Price Too High, Rawlinson declared: “Whenever I had to appear in any case at home or overseas I always insisted that Gordon should be briefed. He was very able”.

The pressures on the Attorney-General’s office meant that the Treasury devil had to appear on his own in court. Moreover, the boundaries of administrative law were being developed rapidly by the English courts and Slynn regularly found himself appearing before the Divisional Court and the Lord Chief Justice, Lord Widgery.

Had it not been for Slynn’s speed and ability to isolate the critical issues of a case, even Widgery, then in his prime, would have struggled to cope with the volume of work. The clarity and objectivity that Slynn displayed in advancing arguments on behalf of government departments meant that the courts were readily able to identify the way in which the law should develop.

Being Treasury devil remains one of the hardest jobs at the Bar. In Slynn’s time, it was also one of the worst paid. He is said to have complained that he did not mind being paid less than leading counsel who appeared against him, but he did object to being paid less than one third of the fee of the junior on the other side.

Slynn performed the role of Treasury devil for six years, which is longer than usual. At the end of that period, he broke with tradition by not moving immediately on to the High Court bench. Instead, he took silk in 1974 and served for two years as Leading Counsel to the Treasury. This meant that he was able to take on private work in addition to his work for the Crown. The experiment of having a senior Treasury counsel was not entirely successful because the unpredictable demands of Crown work and the Government’s insistence that it had first call on his services made it difficult for Slynn to develop a rounded private practice. In 1976, therefore, he accepted an appointment to the Queen’s Bench Division. Aged only 46, he became one of the youngest judges to sit in the High Court.

Two years later Slynn became president of the Employment Appeal Tribunal. With a great many countries displaying considerable interest in the English system of tribunals for dealing with employment disputes, he found himself in demand all over the world to give lectures based upon his experience. His skill at producing a sparkling lecture after a long and arduous journey was much admired.

In 1981 Slynn succeeded Jean-Pierre Warner, QC, as the United Kingdom’s Advocate General at the European Court of Justice in Luxembourg. For the next eight years he shouldered the very heavy responsibilities and workload of a position that is regarded as having the same status as a judge of the ECJ. His opinions as Advocate General were much appreciated by European lawyers for their practical approach, although they were not as theoretical as those of some of his colleagues. Together with Lord Mackenzie-Stuart, the British judge on the court, he successfully campaigned to have greater importance attached to the oral argument stage of the ECJ’s proceedings. This was to the considerable advantage of the British advocates who, by dint of their training, were better able to deal with the cut and thrust of oral argument than their European counterparts. In 1989, on Mackenzie-Stuart’s retirement, Slynn became the British judge on the European Court of Justice. By then, he would have welcomed a return to the English judicial scene. However, his contribution in Europe was too valuable and the ECJ had the benefit of his considerable ability for three more years. During that time, he became known among the young lawyers of the court as the “juriste de grande vitesse” — by analogy with the French high-speed train.

Slynn returned to the UK in 1992 as a law lord. Six years later he gave a dissenting judgment when the House of Lords decided by a 3-2 majority that the former Chilean dictator Augusto Pinochet was not immune to prosecution and could face extradition proceedings to Spain. The verdict was later set aside, following the disclosure of Lord Hoffmann’s links to Amnesty International.

Slynn retired in 2002. He took a close interest in Gray’s Inn and managed while a Judge of the European Court to be Inn’s treasurer. His links enabled him to pursue his interest in the welfare of law students and young barristers. He also found time to serve as visiting professor of law, at Durham and Cornell among others. He was an honorary Fellow of University College Buckingham. He took a deep interest in the activities of the International Law Association of which he was chairman of the executive committee and the Union Internationale des Avocates of which he was an honorary vice-president.

Slynn was knighted in 1976, sworn of the Privy Council in 1992 and made a life peer in the same year. He was appointed GBE in 2009.

He was an active patron of several charities, including the Child in Need Institute, founded by his wife, Odile Boutin, to help Indian mothers and children. Slynn is survived by his wife, whom he married in 1962.

Lord Slynn of Hadley, GBE, QC, a Lord of Appeal in Ordinary, 1992-2002, was born on February 17, 1930. He died after a brief illness on April 7, 2009, aged 79