The scene in the division lobby on Tuesday night was a far cry from the merry scenes of a month ago when a mix of Brexiteers, pro-remain MPs and “stop banging on about Europe” Tories came together to back an amendment calling for changes to the backstop. The hope had been that the unlikely coalition that came together that night would hold firm and vote for May’s revamped deal when it was returned with changes on the backstop. In the end, May did win some legally binding changes but they weren’t enough to keep this motley crew together. Her deal was defeated by 149 votes, with 75 Conservatives voting against. Those MPs – a mix of hardcore Brexiteers and ultra remainers – were the subject of fear and loathing from their party colleagues on a long and tense night in parliament.

One cabinet minister was overheard in the voting lobby saying that they could “fucking spit” on the MPs voting down the deal. Other ministers were quick to repeat claims that their Brexiteer colleagues are kamikaze MPs who wouldn’t be happy with anything.

To say relations in the Tory party are at a low ebb would be an understatement. Yet by the end of the week, you can expect things to be even worse. By voting down May’s deal, Conservative MPs have sparked a chain of undesirable events. First MPs will vote to try to take no deal off the table. Then they will vote to try to delay Brexit by seeking an extension to article 50. The expectation is that both votes will pass. What remains unknown is how much damage the process would inflict on the Conservative party. The concern in government is that it will be huge.

There will be no hiding place in these votes, which will bring longstanding divisions to the surface. A free vote on no deal means many cabinet ministers who vote in favour will become alien to those remain-leaning MPs who believe it must be stopped at all costs. For over two years, the prime minister has attempted to act as a unity candidate, bringing together the leave and remain forces in her party. The general view was that if the party could pass a deal – however painful that process would be – they could then draw a line, install a new PM free of battle scars and stop banging on about Europe.

That idea is now for the birds. With an article 50 extension looking likely, even the departure of May would not resolve the issue of Brexit, which would dominate the ensuing leadership contest. There is a concern among backbenchers that the path May now finds herself on could lead to a permanent split in the party. There are no good options left for the prime minister or her party.

May will not want to go down as the Tory leader who split the party in two. This is why some ministers wonder whether, with no Brexit breakthrough, the UK will head to a public vote. “Were she to do as the remain forces in cabinet want and move to a softer Brexit position, it would split the party,” says one Brexiteer who voted for her deal. “She won’t do that.”

May is also unlikely to plump for no deal. If she did that, there would be mass resignations from her cabinet – and potentially a rush of backbench MPs quitting to join their former pro-EU colleagues in the Independent Group. If May cannot bring about a third vote on her deal in which it passes, a general election may be seen as the least worst way out. But with no agreement on what will be in the manifesto or who will lead them into it, it’s anyone’s guess what will happen next.

Some have even begun to think the unthinkable – that a spell in opposition might give the party the breathing space its members need to recharge and rediscover what they have in common. “We can’t go on like this,” sighed one backbencher. The threat of Corbyn means that for most MPs, however, the only option is to keep on marching forward in the hope that something turns up. But with both sides moving further apart, this week could go down in history as the point in which some form of split became inevitable.

• Katy Balls is the Spectator’s deputy political editor