It is the Tory Europhiles who have returned from their Christmas break determined to assert their will on the government.
On the face of it, the defeat does not stop much and would not prevent a no deal. But it is the starting gun on what will be weeks of parliamentary trench warfare supported by elements even within the Conservative government.
The result of the vote - a defeat by seven with 20 Tory MPs rebelling, including former cabinet ministers Sir Michael Fallon and Justine Greening - is one thing, and a bad introduction to the resumption of the "meaningful vote" debate.
But the manner of the debate beforehand was quite something else.
Sir Oliver Letwin, the doughty defender of the government on Article 50, made matters extraordinarily clear.
"It is the precedent that this amendment sets, which is that on any power taken in any bill in relation to the exit of the UK from the EU, if there is a majority in the house today and there continues to be majority against no deal, it will be possible to bring forward similar amendments," he said.
"It is my proposal that we should indeed do that. I want to make it abundantly clear to those of my honourable friends who are thinking of voting against the prime minister's deal, which I shall be supporting, that the majority in this house, if it is expressed tonight, will sustain itself, and we will not allow a no-deal exit to occur at the end of March."
The former cabinet office minister, in charge of civil resilience, was withering about the no-deal planning he advocated.
He said MPs could not "responsibly impose on our country a risk that may be severe of serious short-term disruption", and that he would continue to oppose the government until March to "put paid to this disastrous proposal".
MP Nick Boles was also withering about the deficiency of no-deal planning, saying that the government had prepared for it "woefully" and that MPs could "on no account countenance a no-deal Brexit".
He said he would vote on "any motion, on any amendment, on any piece of legislation" that ensures Britain either leaves the EU "with a deal or not at all".
There are a further 20 Tory MPs who have publicly indicated they are against no deal, and there are also a large number of ministers who would resign rather than let it happen.
How exactly they stop it is another question - no deal is still the default option.
For now it seems likely that Number 10's inevitable efforts to leverage this vote to persuade Brexiteers to accept the deal will not work next week at least.
But the government could be rendered ridiculous with repeated defeats until it volunteers to abandon no deal.
Eventually, some might be tempted to try to bring down their own government if it chooses to adopt no deal as a policy.
On Tuesday night the rebels showed they were serious about a new parliamentary red line against no deal - and it has been obvious since the day after the 2017 general election that the numbers are not there for this option in the Commons.