IF a week is a long time in politics, a decade feels like an eternity.

In 2006, Labour was 18 months into a third term at Westminster following another comfortable victory over the Conservatives. Tony Blair’s party was also in power in Cardiff, Edinburgh and London.

It seemed like the New Labour project to reframe British politics had worked. Elections were fought against a backdrop of investment in public services versus Tory cuts. Labour was winning easily.

Ten years later, come 2016, the compass that provided a route map for progressive politics has been broken. Labour still has Wales and London, but there seems to be more chance of Jeremy Corbyn skateboarding to the moon than there is of him becoming Prime Minister.

The centre-left used to control the narrative, but the lesson of 2016 is that the political agenda has been seized by different forces. Immigration and identity have superseded the moderate centre-left agenda pursued during the Blair-Brown years.

Historians could look back at life in the UK in 2016 with a sense of deja vu – sluggish economic growth, debates over military action in far-flung lands, England flopping at a major football tournament. It may seem odd to say, but, in some ways, 2016 was a remarkably average year.

Only one event truly stands out. It was the event that delivered the biggest smack in the face to the established political order in decades. It was also the event that lowered sights, narrowed minds and made us roll around in the gutter, rather than reach for the stars.

By voting for Brexit in June, 17.4 million people not only backed an end to a four decade-long union with our European neighbours, but they also hit the nuclear button on a process that will have far-reaching economic consequences for decades to come.

Most political events described as seismic rarely turn out that way, but Brexit will be momentous. Living in the UK over the next five years will be like being trapped in a prison cell where you are forced to listen to the sound of politicians you do not like endlessly debating a process you know will go badly.

The June referendum on the UK’s membership of the European Union was a disaster for progressive politics. Remain – a jaded crew of political leaders, big business representatives and trade union bosses – ran a lacklustre campaign that failed to connect emotionally with voters.

Leave, on the other hand, pursued a strategy that veered from the dishonest – lies about £350 million a week extra for the NHS – to the disgraceful, which came in the predictable form of a racist billboard implying that Brexit would stop black refugees from entering the country.

In a depressing but entirely foreseeable spectacle, the EU referendum became an up-and-down-vote not on our place in the EU, or, laughably, David Cameron’s meek welfare renegotiation, but on the ultimate wedge issue that makes progressives nervous: immigration.

However, politics is the votes business and the winner reaped the spoils. After June 23, the UK had no option but to pursue one of the messiest divorce settlements in history. It also ended Cameron's career and ushered in Theresa May as Prime Minister.

As 2016 slips from view, Brexit’s most profound effect is on a UK political system that has largely remained intact since the second world war. Two issues that were once the preserve of cranks and oddballs now dominate political discussion, the European Union and immigration.

The EU was for decades the favoured subject of Tory pub bores, turning off floating voters who saw this bizarre obsession as evidence of an out of touch party. In 2001, William Hague fought the UK general election campaign on the basis of “saving the pound”. Labour won with a majority of 167.

Immigration has always bubbled under the surface at elections, but Labour and the Conservatives have, to varying degrees, refrained from stirring up problems with race relations. Michael Howard dipped his toes into the immigration waters in the 2005 election, but he, like Hague, received a decisive rejection from the voters.

These fringe issues have moved into the foreground and are the new mainstream. Cameron concluded that an EU referendum was a way of healing divisions in his own party, but he ended up shifting the terms of political debate onto terrain he always wanted to avoid. Brexit was a three-way conversation between the Tory Right, an emboldened UKIP and socially-conservative Labour voters. Progressive politics and the Big Society were nowhere.

Data by the social research institute NatCen reveals just how deep the problem of the Brexit legacy is for the centre-left. Around 80 per cent of people with no formal educational qualifications voted for Leave, as did 70 per cent of folk living in council houses. Around 66 per cent of people earning less than £1,200 a month backed Brexit, while a majority on less than £26,000 a year did likewise. In other words, Labour voters were key to victory.

Consider the Tory record this year. The UK Government foisted a referendum on the country that few people wanted, dividing families and workplaces. It created a culture of intolerance towards immigrants, cost a Tory Prime Minister his job and led to a hilariously bitter succession battle. No route map for Brexit has been produced and May’s government is paralysed by leaks. And, yet, despite all these traumas, the Tories lead Labour by between 11 per cent and 17 per cent in the polls.

The Conservative’s apparent march towards a bigger Westminster majority is the most visible sign that politics has moved to the right. After the EU campaign, Labour MPs tried to oust their left-wing leader Jeremy Corbyn on account of his low profile during the referendum and his general under-performance since succeeding Ed Miliband.

The contest symbolised the reasons behind Labour’s decline. Instead of talking about key issues voters cared about – immigration, social security and economic competence – Labour embarked on an interminable, two-month bout of navel gazing that gained left-wing members but alienated hundreds of thousands of ordinary voters.

Brexit accelerated a process that was already underway for Labour. Centre-ground voters who were vital to previous Labour general election victories had already gone, but they were joined by working class voters attracted to the UKIP agenda. The Tories are winning by default because Labour has left the pitch to have a row with itself in the dressing room.

Labour should look to the independence referendum for an explanation as to what is happening. Although the Yes side lost the vote in 2014, Alex Salmond and the SNP successfully re-set politics north of the border so that the constitution mattered above all else. Scottish Labour was unable to adapt to this new political environment and is sliding towards annihilation. If UK Labour resembles the walking wounded, Scottish Labour is more like the Walking Dead.

Similarly, few people join the Labour party to debate the European Union or immigration. A referendum on the EU, as was the case with a plebiscite on independence, is the equivalent of Labour playing a football match away from home in a hostile, unforgiving environment. The Tories, despite all their rows and melodrama, are comfortable talking about Brexit and borders. Voters sense this and act accordingly.

More broadly, the traditional two-party system no longer seems fit for purpose. Labour and the Conservatives have always been coalitions, but the loyalties that tied disparate interests together appear to be unravelling. UKIP, even with Nigel Farage’s resignation, is part of the political furniture in England and Wales and the SNP continues to dominate in Scotland. It seems inevitable that the 'first past the post electoral system', which was fine for the 20th Century, will come under increasing scrutiny.

So what will 2017 bring? If you enjoy constitutional politics, this could be a bumper year. Expect endless debates in the media and in Parliament on the intricacies of the UK leaving the EU. Theresa May will also trigger Article 50, a process that will make the theory of withdrawal a reality. Nicola Sturgeon will use her political leverage to dangle the prospect of a second independence referendum.

On paper, 2017 should be a tough year for a Prime Minister who is new to the job. She will have to negotiate with European partners who resent the UK wanting to leave the club but still enjoy the benefits. She will also have to make tough choices with limited resources against a worsening economic background.

The reality is that the stars are aligning in her favour. She will put the restriction of freedom of movement at the heart of her EU strategy – a key voter concern. A looming boundary review that increases her party’s chances at the next election will also draw closer. And she faces an Opposition leader who shows no sign of connecting with anyone outside of the left-wing. Her party’s huge lead could easily grow.

Politics is now marked by anger, bitterness and division. Progressives have not lost their voice, but 2016 showed that voters are choosing not to listen.