British politics has long been seen as steady and sensible. Not any more.

Hundreds of British MPs took the biggest political gamble that anyone has seen in living memory. The stakes have never been higher in peacetime.

With just over two months to go until the UK is due to leave the European Union, politicians from all sides — Conservative, Labour, Liberal Democrat, nationalists, unionists — voted down the deal painstakingly negotiated by Prime Minister Theresa May over the past two years.

Some voted against Mrs May because they want Britain to crash out without a deal. Others voted because they want a better deal. Still others because they want to prevent Brexit altogether.

In among all the chaos that will follow, only two things are certain.

First, that they can't all get their way. In a few weeks' time, some of those politicians who cheered the result will be very disappointed indeed.

Second, that in voting down the only deal that was available, they have made a more extreme outcome more likely.

Nobody saw this coming

Theresa May painstakingly negotiated the Brexit deal over the last two years. ( AP: House of Commons/PA )

The time for any plausible compromise is fast approaching the end. Britain is far more likely now than it was 24 hours ago either to be left without a deal or been forced to have to abandon Brexit altogether through a second referendum.

Whatever they may say now, nobody saw this coming at the beginning of the Brexit negotiations.

Throughout the referendum campaign in 2016, all sides presumed that if Britain did vote to leave the country would end up in some kind of long-term relationship with the European Union.

Some on the Leave side even promised that striking a new deal with Europe in the event of a Brexit vote, would be the easiest international negotiation in history.

It hasn't turned out like that.

In part that is due to the simple fact that it is fiendishly difficult for a country to extract itself from a complex legal, economic and political relationship that has built up over decades.

But it is also because British politicians have entirely lost their long-deserved reputation for pragmatism and compromise.

A huge leap into the dark

Conservative Party MP Boris Johnson leads the charge for a harder and harder Brexit. ( Reuters: Henry Nicholls )

The Brexit debate has been characterised by a simply extraordinary level of polarisation.

With each twist and turn, MPs have become more divided, not less, and the leading players' positions have been more entrenched.

Take the case of Boris Johnson. Mr Johnson was once a renowned moderate in the Conservative Party. He famously wrote two drafts of an article for Britain's Daily Telegraph at the start of the referendum campaign, one arguing in favour of Brexit and the other against.

Now, he leads the charge for a harder and harder Brexit, unwilling to compromise even on questions like the border between Northern Ireland and the Republic of Ireland, an issue on which real human lives might depend.

Quite why Brexit has had this effect on British politicians we might never know. It is even less certain where it leaves the country for the future.

There is a palpable sense of crisis in the UK now and it grows by the day.

Everybody knows what British MPs won't vote for: Mrs May's deal or anything like it. But nobody knows what on earth might be able to muster a majority in the House of Commons.

In rejecting the only deal on which the official British Government and 27 other EU nations were able to agree, Britain's politicians have taken a huge leap in the dark and the whole country has been pulled along with them.

Marc Stears, director of the Sydney Policy Lab at the University of Sydney, was chief speechwriter to Ed Miliband during the Labour leader's unsuccessful 2015 UK election campaign.