Taoiseach Bertie Ahern has cautioned members of both Houses of the Westminster Parliament that Britain and Ireland's mutual relations will require continuing priority at the highest political level.
In his historic address to MPs and peers assembled in the Royal Gallery at Westminster yesterday, Mr Ahern also urged them: "We must sustain our hard-won achievements on Northern Ireland.
"Remembering where we have come from, we must never, ever, take for granted the stability and the hope that are now taking root in Northern Ireland."
In a speech celebrating "the most beneficial transformation in British-Irish relations in over 800 years", Mr Ahern told his audience: "The relationship between Britain and Ireland has changed fundamentally for the better. It is and will remain vital for both our countries."
With putative prime minister Gordon Brown listening in the front row, the Taoiseach continued: "The success we have seen - in re-imagining British-Irish relations and in establishing peace in Northern Ireland - is not the end, but only the beginning of what we can achieve together."
Quoting Gladstone, Mr Ahern noted that "the so-called 'Irish Question' was for a long time shorthand in these halls for a nuisance, a problem, a danger. A recurring crisis that was debated here, but not where its effects were most felt."
But he declared: "Today, I can stand here and say that the 'Irish Question' as understood then has been transformed by the Good Friday agreement."
The cross-party audience applauded warmly when Mr Ahern described outgoing prime minister Tony Blair as "a true friend to me and a true friend to Ireland", one with "an honoured place in Irish hearts and in Irish history".
In introducing the honoured guest, Mr Blair had been lavish in Mr Ahern's praise, describing as "formidable" his contribution to the peace process.
"His attitude set unionist minds at rest," said Mr Blair. "He would absorb the harsh, occasionally insulting words. He would remain calm, when around him storms were raging.
"He would be firm when firmness was necessary, flexible when flexibility was essential, and at all times, in every situation, never let his eye stray from the big prize."
Mr Blair went on: "He was a man I could always trust with a vision of the future not just for Ireland but for these islands.
"I often say to people I have met many big political leaders over my 10 years in office but I have never met a bigger one than Bertie Ahern."
Through him, said Mr Blair, "and through the freshly found confidence, even exuberance, that is modern Ireland, these islands have at last escaped their history; or perhaps more accurately answered the call of that history's finer elements."
Fine Gael leader Enda Kenny, who was present for the Taoiseach's address, said it was "a fine speech" which had been well delivered. "It's on with the future now and, if elected taoiseach next week, I will be happy to work with all the public representatives in building on that future for the next generations."
Others among the attendance of about 500 included SDLP leader Mark Durkan, former SDLP leader John Hume, British chancellor Gordon Brown, deputy prime minister John Prescott, home secretary John Reid, former prime minister Sir John Major and past and present Northern Ireland secretaries including Peter Hain, Paul Murphy, Peter Brooke, Tom King and Roy Mason, head of the decommissioning body Gen John de Chastelain, Ulster Unionist MP Lady Sylvia Hermon and Liberal Democrat leader Sir Menzies Campbell.