IN keeping with modern parliamentary tradition, the historic debate over the life or death of the United Kingdom commenced on Andrew Marr's sofa.

On January 8, David Cameron launched a New Year offensive by telling the BBC presenter it would be "desperately sad" if Scotland left the UK, and he wanted a decisive vote on the issue "sooner rather than later".

Caught on the hop, Alex Salmond accused London of trying to dictate terms to Scotland. Ignoring him, Scottish Secretary Michael Moore then kicked off the Coalition's consultation on the referendum 48 hours later by saying Holyrood didn't have the power to hold its own a ballot, as the constitution was reserved to Westminster. If it tried, it could end in a court challenge.

Charitably, Westminster was ready to lend Holyrood the appropriate power, but there were strings attached – the prime condition being a single Yes/No question. Moore's statement was a head-on challenge to the SNP position that Holyrood could run its own vote and also ask about enhanced powers, or devo max.

If the UK Government's intervention was calculated to provoke a response, it succeeded. Later the same day, Salmond announced that his Cabinet had, coincidentally, just signed off its own consultation on the referendum and, by the way, the date would definitely be autumn 2014.

And so began the Great Process War of 2012, a nine-month epic of bluffs and horse-trading. Along the way, both the Nationalist and Unionist sides elevated then abandoned assorted positions. The SNP threat that Holyrood would hold its own referendum rather than put up with London attaching strings to the vote? Dumped. The Downing Street briefings about London holding a snap referendum if Scotland delayed? Silenced.

But before common sense prevailed behind the scenes, there was plenty of bluster out front. With typical modesty, the First Minister launched the Scottish Government's rival consultation on the referendum at Edinburgh Castle on Burns Night to a packed gathering of the world's media. Salmond unveiled the "short, straightforward and clear" question he wanted: "Do you agree that Scotland should be an independent country?" Unionists complained it led people to say Yes.

Almost as significant was the last question of the press conference, when a Spanish reporter asked how Scotland connected to Catalonia, where

economic misery was fuelling calls for secession. Scottish independence, the First Minister said, was "sui generis", a one-of-a-kind with no impact elsewhere; Madrid needn't get in a sweat.

It was a cute reply, but also an early glimpse of an issue which would come to bedevil Salmond, the SNP and the broader Yes campaign – Europe.

February saw a harmless digression into "what if" territory, with the launch of a campaign for devo plus by the Reform Scotland think tank. Sincere but doomed, the cross-party effort to find a compromise between independence and the status quo never took off because not even its backers suggested putting it on the ballot.

The following month, the Westminster consultation closed after 3000 responses, a quarter of them using a "standard text" from the Labour website. It was a sign that neither consultation would be terribly illuminating or useful: Salmond didn't even bother publishing the findings from his listening exercise until a month after he agreed the referendum terms with Cameron.

It wasn't until late May that things livened up again, with the launch of Yes Scotland. Nominally cross-party, but dominated by SNP cash and personnel, the campaign began with Salmond and the Green Party leader, Patrick Harvie, signing the Yes Declaration, while a motley troupe of folkies, poets and choleric actors strummed, sang and foamed at the mouth in an Edinburgh multiplex. The audience loved it, the media crucified it.

A fortnight later, Harvie announced the Greens wouldn't be joining Yes Scotland after all, as it was little more than a vehicle for the SNP. Two weeks after that, the Unionist Better Together campaign made its debut in a former sanatorium, as Alistair Darling painted a picture of an independent Scotland as grey as his soul. Separation as a "one-way ticket to send our children to a deeply uncertain destination" was one of his chirpier rib-ticklers.

After all the build-up, both campaigns then fell oddly silent over the summer as another, slow-burn issue came to dominate the debate. After months of speculation, the SNP leader at Westminster, Angus Robertson, proposed the party should end its 30-year opposition to Nato to reassure voters worried about defence after 2014. For many in the SNP, membership of the nuclear alliance was anathema, and irreconcilable with the party's pledge to remove Trident from Faslane. Around a dozen MSPs began a fight-back and the scene was set for a conference showdown.

In the interim, Nicola Sturgeon took over the referendum brief in a September reshuffle, leading to rapid progress between the two governments. Later that month, the first March for Independence drew around 5000 people to Edinburgh, prompting comparisons with the 1.5 million Catalans who had taken to the streets of Barcelona a few days earlier.

To Nationalist cheers, Labour leader Johann Lamont also announced a review of universal benefits, sniping at the "something for nothing" culture. The SNP accused her of being as bad as the Tories.

October was hectic. The Greens belatedly joined Yes Scotland after securing a seat on its advisory board. Then Cameron and Salmond signed the Edinburgh Agreement, paving the way for a Section 30 order giving Holyrood the power to hold the referendum.

Both sides compromised, but both also had wins. For Westminster, the prize was a single question. In truth, Salmond had been reconciled to dropping a devo max option, as feedback showed there was little public appetite for it. Many in his Cabinet hated the idea too.

The First Minister's win was a referendum immune to legal challenge and with a binding result. Salmond also secured votes for 16 and 17-year-olds and his choice of date by the end of 2014, when the Section 30 order expires.

And so the Great Process War ended, leaving just skirmishes over the role of the Electoral Commission and campaign spending limits as the 100-week slog to 2014 finally got under way. Within days, the First Minister chalked up another score at SNP conference, when an eloquent and fiery debate over Nato resulted in narrow victory for Robertson and the party leadership.

But there was little time to savour it. Within 72 hours, two SNP MSPs quit the party over Nato and all hell broke lose at Holyrood. The spark for the latter was a statement by Nicola Sturgeon in which she conceded ministers had never obtained formal legal advice on the entry of an independent Scotland to the European Union. This was in spite of the Government assuring MSPs and voters that entry would be automatic.

Sturgeon, whose portfolio includes Freedom of Information (FoI), also announced the Government had abandoned a Court of Session action it had mounted against Scotland's FoI watchdog, after it ordered ministers to say if they had any advice.

Salmond was immediately in the firing line. When he had been asked by the BBC's Andrew Neil in March if he had formal legal advice, he had replied: "We have, yes, in terms of the debate." It was to prove a key moment – the moment the gloves came off in the independence debate.

Labour accused Salmond of being a "bare-faced liar", guaranteeing a raft of scathing headlines such as "EU Liar" and "EU're a liar". The tortured explanation for Salmond's comment – that previous Government documents mentioning Europe had been "underpinned by legal advice" because lawyers hadn't objected to them – was as insulting to voters as it was demeaning to him.

"In terms of the debate" became a punchline at Holyrood, a running joke on SNP slipperiness. As the parliamentary exchanges became uglier, the far left tried to raise the tone at the Radical Independence Conference in late November, calling for a new vision of what independence might mean, rather than the semi-skimmed SNP version. The vision turned out to be the high-tax Socialist republic rejected by voters down the ages, but the event still had an energy that was missing elsewhere.

The euro-bogeyman returned in December in the form of Commission president Jose Manuel Barroso. In print and on TV, Barroso made it clear that any part of an EU state which became independent would have to apply afresh for entry and negotiate terms satisfactory to all the other states. In other words, the SNP position that entry would be automatic for Scotland was nonsense.

Forced to react, Sturgeon dropped the automatic entry line and said EU membership would be negotiated through common sense and realism. Instead of inheriting the UK opt-outs on the euro and the passport-free Schengen area, these would be negotiated, along with the UK rebate.

Although it brought the SNP and the Yes campaign to a more honest place, it was a humbling retreat. Better Together claimed the episode showed the Yes side's instinct for "deceit".

With the independence debate starting in earnest, 2012 should have been the year in which the SNP and the Yes campaign began to build momentum. Instead, an Ipsos Mori poll in October suggested support for independence has fallen by almost 10 points since January to 30% and the Unionist attack line that Salmond's vision of independence is based on assertion looks dangerously close to sticking.