The political spotlight was thrown sharply back on the issue of IRA decommissioning last night, following the historic inaugural meetings of the British-Irish Council and the British-Irish Intergovernmental Conference in London.
As the final institutional structures prescribed by the Belfast Agreement came into being, the Taoiseach, Mr Ahern, issued a direct challenge to the paramilitaries, saying: "I think they should assist us in decommissioning the word `decommissioning' - get rid of it."
And while another day of symbolism was capped by a historic first public handshake between Mr Tony Blair and Sinn Fein's Health and Social Services Minister, Ms Bairbre de Brun, the British Prime Minister expressed the general anxiety that the decommissioning issue continues to cast its long shadow over a transformed political landscape. Following the first-ever meeting of the representatives of the British and Irish governments, the Northern Ireland Executive, the Scottish Parliament, the National Welsh Assembly, the Isle of Man government and the representatives of the Channel Islands, Mr Blair said the "best and simplest thing to say" was that the arms issue was being dealt with by the independent commission.
He added: "I believe that people have come so far now, and seen what co-operation and partnership can bring, that I am sure everyone will be working towards making sure that the agreement in its entirety is implemented and that we deliver that peace that people want to see."
Anticipating "reciprocation" by the republican movement, Northern Ireland's First Minister, Mr David Trimble, expressed his confidence that "the better future that people expect to see will not fail to materialise".
Mr Seamus Mallon, the Deputy First Minister, said it was inconceivable that the institutions now established could be allowed to collapse. "There are things in life from which you never go back," he declared.
Mr Trimble hailed the first meeting of the national, regional and island governments as "a truly exciting and challenging development".
In an inaugural session lasting barely two hours, the British-Irish Council approved a memorandum on its working procedures, adopted an initial list of issues for early discussion and decided which administrations would take the lead in each sectoral area in preparation for next June's summit in Dublin.
The five key areas are drugs (the Irish Government); social inclusion (the Scottish executive and Welsh cabinet); environment (the British government); transport (the Northern Ireland Executive); and knowledge economy (Jersey).
An indicative list of other issues which might be suitable for the council's work included agriculture, the marine, health, energy, culture, and tourism.
As the advent of the British-Irish Council symbolised what Mr Ahern called "the widening and multiplying of relationships" that had taken place, the new machinery of the London-Dublin intergovernmental relationship also agreed a list of issues which will form a programme of work.
In respect of bilateral co-operation, these include asylum and immigration; European Union and international issues; and social security, including methods of fraud detection.