Reaction:Northern Ireland is now a place of "peace and promise", Taoiseach Bertie Ahern said today.
Speaking after the Rev Ian Paisley and Martin McGuinness were sworn into their positions of first minister and deputy first minister, Mr Ahern said the "sad turbulent past" could not be undone.
"But we can, and are, shaping our future in a new and better way. And in doing so, we can put the divisions of the past behind us forever," he said during ceremonies in Stormont.
Paying tribute to his opposite number, Mr Ahern added: "Today, relationships on this island and between Ireland and Britain stand transformed. There are many people who have played a part in this vital process.
"But the people of Ireland know that this would not have come about without the commitment and dedication of Prime Minister Blair.
"This was not a process that promised quick or easy rewards. But he has been a true friend of peace and a true friend of Ireland. And for that we express our heartfelt thanks."
Mr Blair also had praise for Mr Ahern in his comments. He said relations between Britain and Ireland during the past decade had been transformed.
"Today we are partners and we are friends. Recently at Croke Park, Ireland and England played each other in an atmosphere unthinkable a few years back."
He joked: "Wrong result, mind you, but a magnificent sentiment."
He said no other premier had shared more cups of tea with him as they toiled through longs hours of negotiations. "But Bertie has always been there, ready to surmount yet another obstacle. By his actions he showed the willingness to engage, to understand and to reconcile. Bertie, thank you," Mr Blair said.
President Mary McAleese said in a message to Dr Paisley and Mr McGuinness that it was "an extraordinary day in the history of Northern Ireland, the island of Ireland and indeed of relations between Ireland and Britain.
"You carry the hopes of everybody as you take forward now the mandate you have been given by the people. I know from what you have both said that you are determined to discharge that mandate to the full, in the interests of all the people."
"For our part in the South, we stand ready, as the Taoiseach has made clear, to work with you in a new partnership that will bring tangible benefits to all the people of the island of Ireland."
Speaking before today's events, Mr McDowell said: "As a liberal Republican I welcome this monumental step on the road towards reconciliation of green and orange. From here on, the two communities in Northern Ireland have the means to focus on the things they share rather than on the things that divide them.
He said he wanted to remember "all of those who gave their lives or who dedicated their lives to the cause of political reconciliation in Northern Ireland.
"While the tide of events may have flowed past some of them, their contributions and indeed the contributions of all those who have suffered for their beliefs and at the hands of the paramilitarists should be remembered on a day like today."
Northern Secretary Peter Hain said the "personal chemistry" between Dr Paisley and Mr McGuinness is "very good".
He said: "I have been hugely impressed with their determination and their businesslike approach to really getting on with the job.
"There's been more preparation for this moment done between the DUP and Sinn Féin, between Ian Paisley and Martin McGuinness and their ministerial party colleagues than ever before, and that's what fills me with optimism as well - not just that the darkness and horror of the past is now behind us - but that there is a real prospect of this government working," he added.
Fine Gael leader Enda Kenny said devolution was "the result of the work of many governments and political parties on both sides of the Border.
"Personally, I am particularly proud of the role played by my predecessors as leader of Fine Gael, both in government and in opposition.
"I look forward to working closely as Taoiseach with the new Executive to realise the full economic and social benefits of lasting peace on this island."
