Saturday will be the most momentous moment in British peacetime politics

Pro-European MPs are still finalising their plans. One idea is to reject the deal until and unless legislation passes; another is to fight for a referendum tomorrow. But whatever precise mechanism is decided, we must stop the deal

When people look back in future generations, will they say this was one of our finest hours, or one of the darkest? Will it be the moment when we stopped the madness of Brexit or when we amputated ourselves from our continent?

Tomorrow is a defining moment in our nation’s history, both in parliament and on the streets. MPs will vote on Boris Johnson’s terrible sell-out deal. And hundreds of thousands of people will march on Parliament Square in favour of a Final Say referendum.

This is our chance to make a difference. We can defeat the Prime Minister’s deal; we can force through a People’s Vote; and we can then win that referendum and stay in the EU.

Pro-European MPs are still finalising their plans. One idea is to reject the deal until and unless legislation passes – at which point they could push for a referendum. Another is to fight for a referendum tomorrow. But whatever precise mechanism is decided, we must stop the deal and then go to a Final Say vote.

Our future is on a knife-edge, so everybody must do their bit. Lobby your MP; turn up at tomorrow’s march; bring your friends and family. People power can really make a difference.

Johnson has negotiated an even worse deal than Theresa May. He has turned Northern Ireland into a colony of the EU and plans an extremely hard Brexit for Great Britain – out of its customs union and single market. About the only good thing that people can say about his deal is that it gets Brexit done, and even that isn’t true. This is just the first stage: the divorce. We will be negotiating our future relationship with the EU for years. The only way to get shot of Brexit is to stop it entirely.

If the prime minister really believed he had done a good deal, he would put it to the people in a referendum, but even he is sick and tired of Brexit. He wants to talk about the NHS, schools, more bobbies on the beat and investment in infrastructure. And he’s right. We desperately need to fix our country. But Brexit is no solution to these problems. It will make them worse.

Johnson’s deal will thwack the economy and so knock the public finances by up to £49bn year, according to a new report by The UK in a Changing Europe. Think of how many hospitals and schools we could afford if only we stay in Europe.

It's not just about money, though. Politicians will be obsessing about the fallout from Brexit until the cows come home. The best way to get them to focus on the real problems Britain faces is just to stop Brexit.

Let’s also remember the value of Europe, too – what I call the four “Ps”: peace, power, prosperity and people. The EU underpins peace throughout our continent. It is not something far away or in the distant past. It is here and now. Removing borders has helped foster peace in Northern Ireland. Europe leverages our power on the world stage. Our alliance with 27 other like-minded countries lets us stand up to bullies anywhere, whether Donald Trump or Vladimir Putin. It also means we can make a bigger difference in the big global challenges such as the battle to stop our planet succumbing to climate change.

Then there’s prosperity. We do half our trade with the EU. We virtually created its single market. And as part of the world’s biggest economic bloc, we have cut advantageous trade deals with countries across the world. The EU underpins European people’s opportunities and rights. We have the freedom to live, work and retire in 27 other countries – and strong workers rights, consumer protections and environmental standards as a result.

Sure, people are exhausted. The battle has been going on for almost four years. But this is no time to flag.

We can stop this madness. Yes we can.