Sir David Attenborough, eat your heart out. You may travel to the most exotic biosystems on our planet, but you will be unlikely to glimpse such surreal couplings as we have just witnessed in the voting lobbies of the House of Commons. There was Jeremy Corbyn putting his name to the legislation of Theresa May. There was John McDonnell fusing with Boris Johnson. Most miraculous to behold, Diane Abbott, mercifully recovered from the headache that was so life-threatening that it prevented her from participating in earlier proceedings, marched in step with Michael Gove. Voting together and voting for a very hard form of Brexit. Which meant that it wasn’t even close. The Brexit Bill smashed through the Commons unamended and by 494 votes to 122, a crushing government majority of 372.

This is remarkable at several levels. For all the chatter about obeying the will of the people, how MPs voted was wildly unrepresentative of what the country did last summer. Had the narrowness of the 52/48 referendum result been replicated in parliament, the government’s majority would have been a much more modest 26. It was also dramatically out of sync with the actual beliefs of most MPs, since three quarters of them did not want to leave the EU. Not only did they sign off on Mrs May’s plan to initiate divorce proceedings next month, they did so having been forewarned by the prime minister that she will pursue a very stark and high-risk version of Brexit.

Britain is departing the single market and most likely quitting the customs union as well. She had even told them in advance that she is prepared to crash out of the EU with no deal at all. That this could be in the range of potential outcomes would have horrified most MPs six months ago. It still does so. Yet they waved it through with the salute of a stonking majority. Finally, and very significantly, parliament didn’t even claim for itself any meaningful input when Mrs May enters the negotiating chamber with the EU.

This self-emasculation by MPs at such a momentous juncture in our history requires examination. We need to step back and ask how we got from June to here, how we travelled to the point where a thumping majority of parliamentarians, including so many Labour MPs, gave a mandate to the prime minister to pursue a negotiation strategy in which most of them don’t believe and which the majority think will end with calamity for Britain. If it all goes horribly wrong, this is a question that is going to preoccupy historians and blight the reputations of all but the minority who tried to stand in the way of the juggernaut.

This was not an outcome written in the stars or fated by the gods. It was not even ordained by the 52% of voters who tipped the referendum result to Out. By narrowly voting to leave the EU, the country answered one question, but in doing so it raised a host of other questions about the precise shape that Brexit should take. This was up for grabs. The hard Brexiters understood that instantly. They didn’t stop campaigning when the referendum result came in. They continued agitating and with a burning ferocity that was amplified by the Brexit press at its most megaphonic. They did so to ensure that they could impose their interpretation of what the referendum meant.

Softer versions of Brexit were framed as a “sell out” and a “betrayal”. Any suggestion that parliament had a right to place conditions on how the government approached the negotiations were blackened as “wrecking tactics” to thwart “the will of the people”. While the hard Brexiters were busy stretching the meaning of the referendum to fit their desired outcome, the stunned Remainers were still winded from their defeat. Slowly, those who wanted to preserve a close relationship with our neighbours began to get their act together. Campaign groups were organised. Learned papers were written. Alternatives to hard Brexit were mooted. But they lacked the organisation, the energy and the unity of their rivals. They were badly handicapped because there never was a coalescence around one agreed version of soft Brexit to compete with the hard-core model.

This shaped the context in which Theresa May made her calculations. Milder versions of Brexit were considered inside Number 10, but discarded because of the belief in Mrs May’s inner circle that they would end up with a messy “halfway house”, a compromise that would ultimately please no one. Once she had decided to prioritise immigration control over every other consideration, she was remorselessly driven to the hard Brexit position of quitting the single market. This upped the risk of it being a long-term economic disaster, but had the short-term political merit for her of simplicity and clarity. It was also the line of least resistance in terms of the Europhobic media and the hard-Brexit constituency within her party. The majority of her cabinet were Remainers. Some of them were ardent Remainers, including the home secretary and chancellor. Around about half of all Tory MPs were Remainers. They were cowed by the atmospherics created by the hard Brexiters and scared of a prime minister whom they have learned to cross at their peril.

Whenever a mutiny seemed to be brewing, Mrs May proved adept at confecting a concession that turned out not to be a concession at all. There was a clamour for a white paper detailing her objectives. So a white paper was rushed out. It revealed next to nothing new about her negotiating plan, but it did make it a little bit easier for potential Tory rebels to wrestle their consciences into submission. There was a demand that parliament have the final say on the eventual deal. So parliament was told it would be consulted, but only on a take-it-or-leave-it basis, which will force MPs to accept whatever Mrs May comes back with, even if the terms are atrocious for Britain, because the alternative would be worse. A government seriously committed to involving parliament would have granted MPs a decisive verdict on the outcome of the negotiations and the power to send ministers away to try again if the deal wasn’t good enough. A parliament serious about asserting its rights would have insisted on such a guarantee.

On the crucial amendment that would have secured parliament a real say, just six other Conservative MPs joined Ken Clarke in defying the Tory whips. The feebleness of most of the Tory pro-Europeans was related to the continuing disintegration of the Labour party as it daily finds fresh ways to fail as an opposition. We now have an opposition in which a three-line whip is busted even by whips. To be fair to Jeremy Corbyn, any Labour leader would face a horrendous dilemma over Brexit because of the way it has split the party’s electoral coalition. Even the most skilled of leaders would be struggling to bridge that division. Mr Corbyn has made it so much worse because of his many other weaknesses. He has lost old friends and not replaced them with any new ones with his unwise tweet declaring “the fight starts now”. That has provoked a lot of grim mirth among people who would have liked to see some fight from him when it might have counted: during the referendum campaign or in the parliamentary struggles of the past fortnight. His dire approval ratings and massive poll deficit with the Tories suggest that Mrs May would win, and do so handsomely, any time she contrived to engineer an early election. That provided another reason for Tory MPs not to be brave.

It does not take too much imagination to see how a stronger, more plausible Labour leadership, one clear and consistent about its objectives and commanding the confidence of the parliamentary party, could have done a better job of squeezing concessions out of the government about the shape and the mechanics of Brexit. The Labour leadership essentially sold the pass the moment it declared there were no circumstances in which it was going to block or even just delay the triggering of article 50. That told the government that it could behave pretty much as it liked; it warned any Tory MP thinking about rebellion that joining hands with the opposition would most likely prove a futile gesture and a pointless sacrifice of career prospects.

The legislation now goes to the House of Lords after parliament’s half-term break. Peers are heavily opposed to hard Brexit and the government has no majority on the claret benches. There will be some activity around the issue of the rights of EU citizens already living and working in Britain. But what MPs have done makes it very much less likely that peers will put up serious resistance to the government over its negotiation timetable and strategy. The size of the Commons majority backing the government will intimidate the unelected house.

Parliament will not be entirely voiceless over the next two years. MPs will retain their inalienable rights to comment and question, to carp and moan, to quibble and quarrel. But they have left themselves essentially powerless to influence the outcome of the most important negotiation in Britain’s postwar history. MPs will be allowed to yap. As the juggernaut crashes on.