The Liberal Party shocked itself when it elected Tony Abbott as leader this week.

The man who had masterminded the coup to destroy Malcolm Turnbull was Nick Minchin, the godfather of the Liberals' conservative wing.

As soon as the results were announced – Hockey was eliminated in the first round of voting, and the final ballot was won by Abbott over Turnbull by a single vote – Minchin walked across to a shocked Joe Hockey.

They had not even left the party room. Astonished members were milling about. A gang of reporters was waiting outside. "If I'd known how it was going to go," Minchin told him, "I would have slung you another 10 votes."

Minchin was speakingpartly in jest. He was rebuking Hockey for failing to do his numbers, for bungling his run at the party leadership.

But he was also partly serious. Minchin had not expected Abbott to win. Nobody had expected Abbott to win. Not even Abbott. Contrary to widespread impressions in the media, Minchin did not even want Abbott to win.

Although the pair are both stalwarts of the conservative group in the party, Minchin knew very well what everyone else in the room knew – that of the three leadership candidates, Abbott was the most unpopular.

The parliamentary members of the Liberal Party had just chosen to elect a leader that most of them considered to be unelectable.

Now they had replaced Turnbull, a man nominated as preferred Liberal leader by 32 per cent of voters in the Herald's Nielsen poll,  with a man preferred by only 20 per cent.

Minchin's main aim was to dump the Liberal Party's support for an emissions trading scheme. He had been adamantly opposed to an ETS ever since he took the job of industry minister in the Howard government in 1998.

His voice had been dismissed in the cabinet when Howard decided to support an ETS in 2007. Now he was getting his way.

He would have allowed Malcolm Turnbull to stay in place if he had yielded. He had delivered his ultimatum to Turnbull five days earlier.

Minchin and Abbott had gone to see Turnbull in the Opposition leader's office in Parliament House.

There was a huge reaction against the ETS from the grassroots of the party, they said. They pleaded with him to oppose the ETS or, at the very least, to defer it.

Turnbull was unmoved. "I've got a partyroom decision in favour of the policy and a spill [motion to declare the leader's position vacant] against me failed just yesterday. Why would I back down on something I believe in?"

The two then said that they had no option but to resign from the frontbench, and they detonated a series of orchestrated explosions along it as well, as one after another, other shadow ministers resigned. By the end of the process, Turnbull had lost 14 of his frontbench. He could not limp on.  Another spill motion was to come.

The right of the party had lost that week's gambit. On numbers compiled by the Liberal Whip, Alex Somlyay, the shadow cabinet had approved Turnbull's position to support the ETS by 14  to 6; the Liberal party room had supported it by 47 to 32; and the Coalition party room, including the National Party, was in favour of it by 47  to 46.

But Minchin would not accept defeat. If Turnbull would not submit, he would find a more amenable leader.

Minchin wanted to install the avuncular Joe Hockey instead.

This was logical, but also perverse. Logical because Hockey was the most electable, preferred by 36 per cent of voters as Liberal leader.

And perverse because Hockey had been a solid supporter of the ETS policy. Indeed, he had urged it on the Howard government when he had been the acting industry minister in 2002, five years before Howard adopted the idea.

And Hockey was also a firm friend of Turnbull and an unwavering supporter of his leadership.

To be installed as leader, Hockey would have to dump his commitment to an ETS, and his loyalty to Turnbull. Turnbull and Hockey were the Liberals' leading moderates, as distinct from the conservatives.

Yet that was the deal that Minchin now offered him. It was the same deal that he had offered Turnbull – defer or defeat the ETS, and I will give you the crown. This was the Faustian bargain.

"My whole political currency is as a straight talker," Hockey agonised with supporters. "I will be destroyed."

Hockey was confident he would carry the numbers in a leadership ballot. He didn't agonise over the votes. He didn't even agonise so much over disloyalty to Turnbull; he had promised not to challenge his friend, and he would keep his word, at least in a technical sense.

He would only stand for the party leadership if it was first declared vacant in a spill motion.

No, Hockey agonised over the ETS. Parliament resumed on Monday. The ETS bills were still pending in the Senate. A partyroom meeting was due on Tuesday. A leadership spill was a certainty. What would Hockey do?

First, he went to see his mate, the defiant leader. He told him that he didn't think Turnbull could win. I accept that, replied Turnbull. If the leadership is vacant, said Hockey, I will stand.

Well, righto, came the leader's response. Hockey had the clear impression that Turnbull had said that, if defeated in the spill, he would not then stand in the next ballot, the vote on the leadership.

This was logical. Because a lost spill, for a leader, is effectively a motion of no confidence. What's the point in then standing again two minutes later?

Next, Hockey convened a big meeting in his office about 4pm. It was, essentially, everyone in the leadership group except Turnbull.

Minchin and one of his close conservative allies, Eric Abetz were there. So was  Abbott. So was a Hockey lieutenant, Christopher Pyne.

The pro-ETS Greg Hunt was there, and so was the anti-ETS Andrew Robb. Turnbull's deputy, Julie Bishop, was in the room. So was a conservative mooted as her replacement, Peter Dutton. Even the federal director of the Liberal Party, Brian Loughnane, was present.

Hockey announced that he would stand for the leadership once it was vacant. Then he announced his policy on the ETS. Hockey would not have a policy, he said to an incredulous room.

It was simply too divisive. So he would allow party members a conscience vote in the chambers of the Parliament.

The group broke up to think  about it, and reconvened in Hockey's office a little after 6pm. Hard positions had now formed. Minchin and Abetz opposed the idea of a conscience vote.

Minchin said it was "crazy" from Hockey's point of view, that it would look weak. "Your first decision as leader would be no decision."

One participant, and recollections differ over who it was, observed that under this plan, the ETS would probably pass through the Parliament – "we will have changed the leader and have the same policy!" he expostulated.

"What does the right get out of that?"

Hockey replied: "The right gets Dutton as deputy, me as leader, Abbott as shadow treasurer, and Julie Bishop in foreign affairs." No one had broached with Bishop the idea that she would lose the deputy's slot.

"Joe," said Bishop, "before you start speaking about the deputy's job, speak to me." It didn't come up again.

Minchin argued repeatedly that Hockey's position was ridiculous – you can't have a policy of not having a policy, he said.

At this point,  Abbott declared his hand. "This is an impossible situation for the colleagues," he said.

"Some want to vote for the ETS, some want to vote against it. You can't leave it unresolved. The party has to be offered a clear choice." If Hockey would not change his mind, said Abbott, he would stand as the anti-ETS candidate.

About 8pm, Minchin visited Hockey once again. Abbott joined them. Minchin tried once more to find a way to kill the ETS but install Hockey as leader.

He offered a new formula – a secret ballot on the ETS offering three options – in favour of it, against it, or in favour of a conscience vote on it.

Hockey was ready to accept this, but Abbott would not brook anything offering a conscience vote  option.

That night, as the candidates counted their numbers, a Hockey lieutenant contacted Turnbull about 8.30pm to make sure of his undertaking to Hockey that he wouldn't stand.

He told Hockey that he had received the assurance and had noted the conversation in his diary.

Yet Turnbull publicly vowed, in the strongest of terms, that he would stand and fight.  At the Tuesday meeting, the leadership was declared vacant with a vote of 48 to 34, a clear dismissal of Turnbull.

Then Bishop, as deputy, called for nominations for the leadership. Turnbull was on his feet instantly, followed a second later by Abbott. Hockey rose a moment later. It was to be a three-way contest.

In the first round of voting, Abbott won 35 votes, Turnbull won 26 and Hockey won 23. With the lowest tally, Hockey was eliminated.

The moderate vote had been split between Hockey and Turnbull. Some had abandoned Hockey because of his equivocal position on the threshold issue of the ETS.  Hockey was shocked.

In the run-off, Abbott beat Turnbull by 42 votes to 41. One vote, unbelievably, was informal. After Minchin's crack about the 10 votes, Hockey replied incredulously: "He's a piece of work, isn't he?" indicating Turnbull. "He promised me he wouldn't run if the spill got up."

Later, he bumped into Turnbull on the flight back to Sydney.  "I'm too angry to talk to you," said Hockey.

Turnbull is adamant that he gave Hockey no undertaking. Both men lost. Turnbull lost his leadership, Hockey lost his challenge, and neither got to keep the ETS that he had supported.

And Abbott was, truly, the accidental leader.