Good news from the bubble of party politics: Britain’s opposition leaders have today decided to engage and cooperate rather than facilitate national food and medicine shortages in nine weeks’ time.

Many commentators suggested that Jeremy Corbyn’s meeting with the SNP, Liberal Democrats, Plaid Cymru, Change UK and Greens would yield little but grandstanding and bad temper. On the contrary, participants have described a positive and constructive session, with further summits planned. Their joint statement stresses the “urgency to act together to find practical ways to prevent no deal, including the possibility of passing legislation and a vote of no confidence”.

The statement represents a long-overdue acknowledgment that an unprecedented crisis must be met with an unprecedented response. Labour is correct that Boris Johnson threatens an abuse of power unparalleled by any British prime minister in modern times. If he is prepared to shred convention, so must his opponents.

Today’s meeting is highly significant for two reasons. First, it demonstrates that, when push comes to shove, politicians who may personally dislike or distrust each other can sit around a table and work seriously, cordially and productively. Second, and more importantly, it highlights that MPs have the means at their disposal to stop no deal. They already had the numbers. Now they are showing the willing.

A no-deal Brexit has always been avoidable if MPs wanted to avoid it. That is because we live in a parliamentary democracy and not Johnson’s personal fiefdom. A legislative approach was always going to be less contentious than a vote of no confidence, because it does not require Tories to vote their own government out of office. With a new law, MPs can force the prime minister to request a new extension. They can demand that he accepts it. They can – and should – legislate for a revocation of article 50 if he fails to accept it or if the EU fails to grant it. Two-thirds of the Commons – like the public they represent – oppose no deal. They will also want to avoid being blamed for no deal. If they unite to stop it, they can – and there is now every reason to believe they will.

Corbyn deserves credit here. He is not a politician famed for cross-party cooperation, but has acknowledged that his proposal to lead a caretaker government will probably fail, and has now invited 116 Tory opponents of no deal to join the dialogue. Perhaps our politicians really have grasped the truth of the moment: Johnson has left no more space for anyone else’s ego. Now is the time for flexibility and collegiality.

Today has also taught us an important lesson about our political system. For the past fortnight, the opposition parties resorted to the zone of greatest comfort: partisan attacks. Labour and the Lib Dems were angrily denouncing each other. Corbyn was refusing to signal any openness to an alternative caretaker prime minister. Other parties were either demanding categorical assurances that Labour would now support remain in all circumstances, or else insisting they could not support Corbyn in any. This was tribalism at its most short-sighted and self-defeating. The only beneficiary was the government.

No deal would be a calamity for our economy, society and democracy. Stopping it must be our absolute priority. But we can go further. Today must mark a comprehensive watershed in how our political parties interact in the national interest. It is possible to maintain a distinctive party identity while recognising, and even celebrating, common ground with others. On the continent this kind of cross-party cooperation is seen as normal and essential. It should not be considered revelatory here. In the end, perhaps Brexit will make us fully European after all.

• Jonathan Lis is deputy director of the thinktank British Influence