The leaders of the new political party launching today were courted for two years to lead the Conservatives in Northern Ireland, it has been revealed.
The crunch meeting came on February 18 just a few days after Mr McCallister and Mr McCrea, both MLAs, resigned from the Ulster Unionist Party.
"All in all we have been in discussions with Basil and John for about two years," said Irwin Armstrong, the chair of the Northern Ireland Conservatives.
He added: "Our discussions with John didn't really become serious until he resigned from the UUP in February this year. When we approached him before that John made it clear to us that he felt a loyalty to his constituency association. Basil was more willing to talk."
Mr McCallister resigned from the UUP live on BBC's The View on February 14 after hearing that the UUP and DUP were to run a joint candidate in Mid Ulster.
He regarded such unionist unity pacts as sectarian.
He said he expected Mr McCrea to resign "within hours" and this happened the next morning. A few days later, on February 18, Mr Armstrong met Mr McCallister.
"There was a formal discussion between myself and John after an event hosted by the Platform for Change think-tank," Mr Armstrong said.
"I told John we saw him as the sort of person we wanted to be the leader of the party and offered him the position.
"We also told him that Basil McCrea could join but not be the leader. He did not tick all the boxes for us I made this clear to John and left it to him to inform Basil, who may not have been pleased."
The next morning, February 19, Mr McCallister told the Belfast Telegraph that "the Tories are in the frame". He also told us that a decision on whether to join the Tories or to form a separate party would not be made "til Easter".
He said: "This will not necessarily lead to a new party though it may do". We published these interviews the next day.
A week later, on February 27, both stated publicly that they had now ruled out the Tory option and would instead form a new party that would be "confident, progressive and pro-union".
Irwin Armstrong handled most of the negotiations but Lord Feldman, the Tory's National chairman, also spoke to Mr McCrea at the Conservative Party conference in October 2011.
At the time, Lord Feldman hoped that Mr McCrea and other members of the Ulster Unionist Party might join the Tories and in November, he wrote to Tom Elliott, the UUP leader, suggesting that the party dissolve.
Prior to that the two parties had an electoral pact called UCUNF, which proved unsuccessful at the polls.
Northern Ireland's newest party, NI21, will be launched tonight and will be led by Mr McCrea, not Mr McCallister. However, Irwin Armstrong says he has still not quite given up on Mr McCallister coming over to the Conservatives in the future.
"We have a lot of respect for John and his integrity and ability to communicate with people. We think he would have made a good leader and if he was to change his mind tomorrow and come to talk to us we would be open to have that discussion," he said.
Asked about the possibility of Mr McCrea joining, he said: "We are always keen to get people to join the party."