In the decades that I have been an MP, it has often felt that importance and relevance have ebbed away from the chamber of the House of Commons. But the atmosphere last night, when we voted to trigger article 50 and begin the process of Britain leaving the EU, was electric. It genuinely felt like a momentous occasion.

The amazing Gina Miller fought hard, endured terrible abuse in order to assert the principle of parliamentary sovereignty. And some people will believe that parliament not only failed Miller but failed in its duty by not voting down Brexit. Many of those people are in my own constituency of Hackney North. Hackney is one of the most passionately pro-remain areas in London, itself a city that voted in favour of remaining in the EU. I received more than 1,500 letters arguing the pro-remain case, the most that I can remember on any subject.

It is sometimes forgotten that here has long been a strand of opinion on the left that was anti-EU. Ancestral hostility to the European Union was reinforced, for a younger generation of leftwingers, by campaigning against the Transatlantic Trade and Investment Partnership (TTIP), a series of trade negotiations carried out, mostly in secret, between the EU and US and the profoundly undemocratic way that Greece was treated within the Economic and Monetary Union.

But I supported remain, campaigned for remain and it is clear that the Brexit that Britain is faced with is not a “Tony Benn” Brexit. It is emphatically a Tory Brexit. Theresa May has made it clear that, in negotiating Britain’s exit from the EU, she is willing to put popular fears and anxiety about immigration above any other consideration including jobs, living standards and the economy. This is a remarkable thing. I do not know of any other popularly elected leader who, outside of wartime, did not put jobs and prosperity first.

The Labour party leadership has consistently rejected the option of simply ignoring or reversing the Brexit vote. Such a thing would have been profoundly undemocratic. More than 17 million people voted to leave the EU. For London “elites” to simply ignore the significance of this would have been wrong. Many people voted to leave who had never voted before. If parliament had simply struck down their vote, why should they bother to vote on anything again?

It was right for the Labour leadership to say that it would not wilfully thwart Brexit. But deciding the strategy beyond that would have taxed the wisdom of Solomon. Most Liberal Democrat supporters are also for remain. Most Tory supporters are for leave. But Labour represents both the most passionately pro-leave and the passionately pro-remain areas of the country. And there were voices within Labour that warned of a Scottish scenario. In Scotland Labour voters, who voted against the Labour line in the independence referendum, have yet to return to voting for the Labour party. And there was some polling which seemed to reveal that the same scenario could play out in the north of England in the wake of Brexit.

We have had a lot of intense discussion within the Labour party about Brexit. In the end the Labour shadow cabinet agreed to vote to trigger article 50 when it came before the House of Commons for its third reading yesterday. I voted in line with that collective decision. As a member of the shadow cabinet, I am a national politician and form part of the leadership of a national political party. The shadow cabinet had to listen to the nation as a whole.

But the vote on article 50 is the beginning, not the end. There is an important fight to be had protecting the rights of EU citizens living here in the UK. The Tory party refused to support Labour amendments to the bill on this subject. But that campaign is not over. In her speech outlining the government’s position on Brexit, May used the word “global” 17 times. But the truth is that a Tory Brexit will be far from internationalist. Labour also has to continue to fight to protect workers’ rights, the environment, jobs and living standards – all of these are threatened by Tory Brexit.

But, above all, Labour has to reflect on why so many millions in post-industrial Britain voted to leave the EU. Flat out lies by Brexit campaigners (remember the £350m a week Brexit would mean for the NHS?) were part of it. Immigration was also an issue. But the answer is more complex than those two things. As the dark shadow of Donald Trump falls over the international stage, it will be on Labour’s understanding and response to the Brexit vote that the future of the party rests.