Ian Paisley, the political firebrand famous for bellowing "no surrender", finally did just that last night, succumbing to internal party pressure and announcing he will quit in May as Northern Ireland's First Minister and leader of the Democratic Unionist Party.

Tributes were led by Tony Blair, who, as Prime Minister, saw in the power-sharing Stormont Executive. Describing Mr Paisley's contribution to the peace pro-cess as decisive, he said: "In the final analysis, he made it happen. The man famous for saying no' will go down in history for saying yes'."

The veteran politician - 82 next month - bowed to the inevitable after weeks of speculation and pressure from within his party, where criticism of his closeness to Martin McGuinness, his Sinn Fein deputy, has been growing - their joking in public has earned them the nickname of "the Chuckle Brothers".

In addition, senior DUP members were unhappy at the appointment of his son, Ian Jr, to the local policing board when he resigned as a junior minister in the executive after criticism of his links to a property developer and a lobbying controversy.

However, last night, Mr Paisley, who will stay on as MP for North Antrim and as an assembly member, insisted he was stepping down under his own steam and in his own time - after an investment conference in Belfast organised by the Stormont Executive. He will have been First Minister for a year, not the four he could have expected.

He said: "I came to this decision a few weeks ago when I was thinking very much about what was going to come after the conference. I thought it is a marker, a very big marker, and it would be a very appropriate time to bow out."

Peter Robinson, the DUP deputy leader, and the Stormont Finance Minister is tipped to succeed Mr Paisley in both roles, but party sources did not discount Nigel Dodds, the Economy Minister.

Their leader was adamant he would not be drawn on his successor, saying: "This is not the Church of Rome. This is not apostolic succession and I have no right to say who will succeed me. The person will succeed me when the mark is on the paper and the ballot is cast."

One DUP source noted: "This is uncharted territory for our party. There has only ever been one leader since our formation and that is Ian Paisley."

Praise for the "Big Man", who for much of his career the uncompromising enemy of Irish republicanism but who eventually led his party into a power-sharing executive with Sinn Fein, came from many quarters.

Declaring Mr Paisley had made a "huge contribution" to political life in Northern Ireland and the UK, Gordon Brown said: "The whole country values and admires the manner in which he has led as First Minister. Bringing a lasting peace to Northern Ireland would not have been possible without his immense courage and leadership."

Bertie Ahern, the Irish Taoiseach, said he had spent most of his political life opposing Mr Paisley but went on: "When it came down to making the Good Friday Agreement work and to having an inclusive executive in Northern Ireland, he made the big moves."

Gerry Adams, the Sinn Fein president, said: "His political career has ended with a good and positive legacy for the people who live on this island."

David Cameron, the Conservative leader, described Mr Paisley as a "formidable figure" while Nick Clegg, the Liberal Democrat leader, said his "pivotal role in bringing peace has ensured his place in history".

Alex Salmond, the First Minister, said he had made "an enormous contribution to the peace process".

Gregory Campbell, Mr Paisley's DUP colleague, who represents East Londonderry, insisted: "We will never see a person like Ian Paisley in our lifetime."