The former Ulster Unionist leader David Trimble has announced he will join the Conservative party.
Conservative leader David Cameron today welcomed Lord Trimble, who will join the Tory party group in the House of Lords.
Lord Trimble said it was a long-term ambition to work with the Conservatives following his resignation from the Ulster Unionists in 2005. As party leader, he worked closely with the John Major government and has long been sympathetic to the Conservatives.
"It's something that's been on my mind many times over the years," Lord Trimble told the BBC Radio 4 Today programme.
"Now that Northern Ireland is settled, I'm free to follow what's been an ambition for many years."
Lord Trimble confirmed he had made the decision to join the Conservative group several months ago but was waiting for the Northern Ireland elections and Stormont power-sharing arrangements to be finalised.
Mr Cameron welcomed the high profile attention to his party. "I am sure he is going to bring a great amount to our party, not just on the subject of Northern Ireland but more broadly on security, terrorism and the constitution and develop the Conservative party for the future," he said alongside Lord Trimble at Westminster.
"It's not every day you can welcome a Nobel prize winner to your party," the Conservative leader added.
Amid speculation Lord Trimble could be 'fast-tracked' into a cabinet post, Mr Cameron said he was not planning a reshuffle "today", but added he was looking forward to putting "all the talents in the party to good use".
Lord Trimble said he has told Mr Cameron he does not wish to rush into a cabinet position, wanting instead to acclimatise to the Tory way of doing things.
His former colleagues in the Ulster Unionist Party (UUP) maintain the move has been amicable. Party leader Sir Reg Empey paid tribute to Lord Trimble's work in Northern Ireland.
"Through his vision and commitment, David, along with others, helped to transform politics here in Northern Ireland," Sir Reg said. "He now brings these qualities to the national stage and I wish him well in whatever role he takes within national political life."
Lord Trimble was leader of the UUP for ten years, during which he was first minister at Stormont and MP for Upper Bann.
In 1998 he received the Nobel peace prize alongside SDLP leader John Hume for their part in the Good Friday Agreement.
In 1999 he went on to become first minister of the new power-sharing executive at Stormont. His leadership was undermined by ongoing struggles with Sinn Fein over IRA disarmament, with internal UUP pressure for a tougher stance against the republicans.
This internal struggle saw the DUP take prominence, with Ian Paisley now set to take over as first minister at Stormont.
Despite his record in Northern Ireland, Lord Trimble lost his Westminister seat in the 2005 election.