To observe the Conservative party at Westminster on Monday was to watch a party that seems closer than ever to falling apart over Brexit. Paradoxically, however, nothing in the politics of Britain’s planned departure from the European Union had actually changed since last week. Theresa May still leads a minority government and a divided party, as she did before the weekend. Talks with the EU remain stalled over the Northern Ireland backstop arrangement, just as last week. Meanwhile Labour remains just as neuralgic about giving leadership to anti-Brexit concerns in the country as before. Many of the essentials remain unchanged, yet something has changed all the same.

That something seems to be the confidence of rightwing Brexiter Conservative MPs that they will get the destructive and comprehensive break with the EU that they crave and are working for. The evidence for this altered mood came in multiple guises. The most chilling was the unusually vicious language which rightwing and Europhobic Tory MPs used over the weekend, under cover of anonymity, to attack Mrs May – that she would be “dead soon”, that the knife would be “stuck in her front and twisted”, that she was “in the killing zone” and that she should “bring her own noose”. These are the words of Tory MPs – male Tory MPs, it can safely be assumed – who have lost sight of propriety and proportion as they rage, not against her but against their own political powerlessness.

There were other signs too. In defiance of the reality of their own lack of numbers and the absence of a unifying Tory leadership candidate other than Mrs May herself, there was renewed talk of a vote of no confidence by Tory MPs against her. A group of Brexiters led by the serially disloyal Iain Duncan Smith chose this otherwise inexplicable moment to travel to Brussels to pretend that they speak for Britain when they do not. Back in the Commons, the pro-Brexit schemer Steve Baker, having put down an amendment to the Northern Ireland bill which aimed to kill the backstop, later had to withdraw it for lack of support. Meanwhile the anti-European MP John Redwood and the pro-European Dominic Grieve, two men who barely seem to belong to the same party any longer, each attacked the government’s approach to Brexit from their diametrically opposed standpoints.

The Tory right and left are both running out of trust in the government’s handling of Brexit. But it is the Tory right where nerves are stretched furthest. There are two contextual reasons for this. The first is Saturday’s enormous march in support of a second vote on the Brexit terms. The size and good sense of that march sent a message that both main parties needed to hear, but which is a particularly lethal threat to rightwing Conservative claims to speak for the public will. The second is the verdict of the most recent YouGov opinion poll. Although the Tories lead Labour in that poll and Mrs May’s ratings are better than Jeremy Corbyn’s, there is little comfort on Brexit, since only 1% of voters think the negotiations are going “very well”, with only 17% saying they are going “fairly well”. Some 71% of the public judge that the talks are going badly. When a government has staked so much of its authority on its ability to deliver Brexit, as Mrs May’s has, that 1% is a doom-laden verdict on the public’s lack of confidence.

Mrs May came to the Commons herself late on Monday to try to restore some calm. She was thorough and dogged in her usual way. But the Tory benches were subdued and sullen. Her MPs sat with stony faces. Her backbenchers asked awkward questions that revealed only anxieties and resentments. Mrs May delivered her well-trailed lines that the finishing line is in sight and that 95% of the Brexit deal is sorted. But she had few supporters. The divisions in the Tory party remained glaring. The fundamentals – that the EU will not agree to her selective Chequers approach and that she lacks the numbers in her party to deliver that kind of deal – remain as true now as before. If she is to deliver a Brexit, Mrs May will have to cave in to the EU and to compromise with the rest of the Commons. The message of this week is that the Tories cannot deliver.