Mr Woodward had been agonising over his future in the Conservative Party for almost a year, confiding his disquiet to the Brentford Labour MP Ann Keen as early as January this year.
The two became firm friends after Mr Woodward made what she considered a brave and passionate speech in support of her Bill to equalise the gay age of consent. After their first meeting the two got together from time to time to discuss a range of issues, including Mr Woodward's worries about his party's increasingly Eurosceptic policies - a pro-European, he did not take part in campaigning for the July European elections having "agreed to differ" with the leadership on policy.
Various anguished discussions with family and friends followed as Mr Woodward struggled to reconcile his politics with the rightward drift of the Tory party.
He is understood to have "loathed" the party conference in Blackpool and was left feeling "totally hostile" to many of the policies his party adopted during the week, most notably the new tax guarantee.
After that week, Mr Woodward's discussions with the other side became increasingly intense.
He spoke to Tom Chandos, an old friend and until recently a Labour hereditary peer, about his feelings.
But it was on 24 November when, after the briefest of discussions, the Shadow Cabinet decided to oppose changes to Section 28 legislation - the laws which prevent local authorities from promoting homosexuality - that the Tory high-flyer began to turn his back on the party he had helped to win the 1992 general election.
Between that day and his now infamous sacking by pager on 3 December, Mr Woodward has made it clear he was told to keep quiet about his opposition to party policy - even being forced to meet Ms Keen and representatives of the Metropolitan Police to discuss the issue in secret.
It was after that meeting, on 29 November, that Downing Street was first alerted to Mr Woodward's dilemma. But by 3 December, Ms Keen and Lord Chandos had both independently made it clear to No 10 that it might be worth getting Mr Woodward in and setting up a meeting between him and the Prime Minister.
In the event, he met Tony Blair that same evening after a brief chat with the Prime Minister's official spokesman, Alastair Campbell.
Downing Street aides said that Mr Blair and Mr Woodward had a long conversation about "principles, integrity, why people go into politics, decency and public service".
"At the end of it, Tony said to him: `It seems to me you are probably in the wrong party'," a No 10 source said.
The Prime Minister advised Mr Woodward to think long and hard about his decision, to talk to his wife and not rush into anything.
The following morning Mr Woodward decided he wanted to see the Prime Minister again, arriving later that day at the No 10 flat for further talks, this time with Peter Mandelson present.
The trio talked about Europe, the tax guarantee and funding for the health service.
"Tony was increasingly of the opinion that he was serious and that he was a pretty bright guy," sources said. But again the decision was delayed until Mr Woodward had been able to talk it through with his wife.
The following weekend the Tory MP was in Berlin for a conference where he met Labour's Lord Puttnam and Baroness Kennedy and the German Chancellor, Gerhard Schroder. He found his views on Europe were more in tune with the Labour Party than the Tories.
The final decision to take the plunge was on 13 December, three days before his third meeting with the Prime Minister - but five days before he told the Conservative leader he was on his way.Reuse content