The Attorney General and Ireland's next EU commissioner has been a Cabinet member for two years, yet has retained an extraordinarily low public recognition level. However, in the light of the political controversies of the early 1990s in which a previous attorney general, Mr Harry Whelehan, was involved, a low-profile Attorney General may be seen by the Government as one doing his job well.
As a barrister, Mr Byrne was also low-profile, but very successful. His rise from a successful legal practice to a senior political level owes almost everything to his relationship with Mr Bertie Ahern.
He became involved in politics in 1972, campaigning in favour of Ireland's accession to the EEC. However, his rise to senior level began in earnest less than 10 years ago when he and Mr Ahern served together on the campaign committee for the late Brian Lenihan's unsuccessful run for the Presidency.
The two began to work closely together on other issues, and Mr Ahern would have appointed Mr Byrne Attorney General in 1994 had he become Taoiseach after the collapse of the Fianna Fail-Labour coalition government led by Mr Albert Reynolds.
Instead, Mr Ahern became leader of the Opposition, and Mr Byrne had to wait three years. He worked closely with Mr Ahern in opposition, advising Fianna Fail on many issues, including its approach to the referendums on bail and on the Maastricht Treaty. He served on the Constitutional Review Group set up by the rainbow coalition in 1995.
Mr Byrne became Attorney General in 1997 at a time when major reforms were being introduced to the Office in the wake of the Brendan Smyth affair. The controversy over the lengthy delay in the handling of the Smyth extradition warrant had led to a major programme of change in the way the Office was run.
Since his appointment, the Office of Attorney General has published annual reports, although the first one was under preparation by the previous attorney general, Mr Dermot Gleeson. He oversaw the completion of changes in the staffing structure and also presided over the upgrading of the Office's computer system.
The political issues in which he has been centrally involved include the establishment of the Flood and Moriarty tribunals and the amendment of their terms of reference, as well as the tough negotiations over fees to be paid to barristers working at those tribunals. He also negotiated the complex issues surrounding the establishment of the hepatitis C tribunal.
He was a member of the Irish delegation at the negotiations leading to the Belfast Agreement last year. He managed the constitutional amendments required for the ratification of the Amsterdam Treaty. He was centrally involved in dealing with the Sheedy case.
Most recently he was the subject of some political controversy when it emerged he had once represented Cement Roadstone Hol dings (CRH) in a case concerning Glen Ding Wood in Co Wicklow in June 1997.
Mr Byrne was appointed Attorney General shortly after that and played the key role in drawing up the terms of reference for the payments-to-politicians tribunal. There have been regular calls for the inclusion of the sale of Glen Ding to CRH in the Moriarty tribunal's terms of reference.
However, Mr Byrne said last week that when his office was considering 29 amendments to the terms of reference of the tribunal at the time of its establishment in September 1997, he informed the Taoiseach in writing that he had acted for CRH.
He had told him that as he might be regarded as having a conflict of interest in relation to the issue, he would refrain from making any comment in relation to an amendment which would have included the sale of Glen Ding Wood in the tribunal's terms of reference.
He was a founder and the first chairman of Free Legal Advice Centres (FLAC) and retains an interest in issues of social equality. As Attorney General he asked to be on the Cabinet Sub-Committee on Social Inclusion established by the Government. In 1989 he was legal adviser to the government review body on social welfare law.
Those who work with him say he is good to his personal staff and displays concern about the implications of decisions for them. "He is ordinary in a very nice way," according to one who has worked with him.
He has a number of interests which take him away from politics and law. He is a regular attender at the Wexford Festival Opera and the cinema. He sails a boat which he and a group of friends bought and renovated, and he also owns a 1979 Porsche which he repaired and refurbished himself.
At the Bar he was not among the most high-profile barristers, being described by one senior colleague yesterday as "quiet and diligent". He nevertheless had a substantial and successful practice, working widely in insurance, planning and arbitration. He did a considerable amount of State and administrative work and was counsel to the Tribunal of Inquiry into the Beef Industry from 1991 to 1993.
He gained significant international legal experience as well, being a member of the International Court of Arbitration from 1990 to 1997. The court is the largest disputes resolution body in the world, adjudicating on major commercial and intellectual property conflicts.
Mr Byrne is a native of Monasterevin, Co Kildare. Born in April 1947, he went to school at Dominican College, Newbridge, Co Kildare. He obtained a BA degree at UCD before studying at the King's Inns. He was called to the Bar in 1970 and to the Inner Bar in 1985.
He married Ms Geraldine Fortune, and they have two sons and one daughter. He lives in Blackrock, Co Dublin.
Asked yesterday at Government Buildings why he gave up a successful legal practice to enter the rough-and-tumble world of politics, he replied simply: "I enjoy it."