Former Ulster Unionist leader David (now Lord) Trimble is set to confirm today that he is quitting his former party in order to join the Conservatives at Westminster.
The former first minister in the North's first powersharing executive was unavailable for comment last night, after news of his intention was leaked to UTV.
The Irish Times understands Lord Trimble concluded his negotiations with Conservative leader David Cameron's office at the end of last week.
The expectation in Westminster circles is that Lord Trimble, a Nobel Peace Prize winner, will in turn be offered a position on the Tory front bench in the Lords.
However, while discussions continued in London yesterday, sources said they thought there might be a delay before the nature of a new position for Lord Trimble became clear.
The extension of the Conservative party's organisation to Northern Ireland means Lord Trimble could not take the Tory whip at Westminster without relinquishing his membership of the UUP, which he led until losing his Upper Bann seat in the 2005 general election.
Former colleagues including his successor as Ulster Unionist leader Sir Reg Empey paid tribute to him and wished him well in his new role as a Tory peer.
Sir Reg said Lord Trimble's decision to join the Tories and get involved in national politics should come as no surprise.
"David's long-standing interest in Conservative and national politics was no secret," the East Belfast Assembly member said.
"Colleagues and seasoned commentators will not be surprised by David's decision to take the Conservative whip.
"Through his vision and commitment, David, along with others, helped to transform politics here in Northern Ireland."
UUP peer Lord Rogan of Lower Iveagh said Lord Trimble's decision to become a Conservative peer was understandable and natural given the links between the two parties.