Tom Watson will tomorrow offer to back Theresa May's Brexit deal on the condition that there's a second referendum.

The deputy Labour leader will take centre-stage at the 'Put it to the People' march in London, and will make the pledge in a keynote speech.

He's expected to say: “Millions of people voted for Brexit and many more millions of people - their jobs, their livelihoods and their public services - are going to be directly affected by this crisis.

"I know lots of them because I represent them in Parliament and I am determined to do the right thing by them now.

“Everyone in this country has been let down by this Brexit process; people who voted to leave, people who voted to stay, people who didn’t vote or were too young to vote.”

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He's expected to say he had "reluctantly" come to the conclusion that the only way to resolve the Parliamentary logjam and maintain "legitimacy" in the eyes of the public.

"It can only bring closure if we're all involved in making the decision," he is expected to say.

"It can only begin to bring the country back together again if we all have a final say – and then live with the result."

And in a direct message to the Prime Minister, he will say: "I will vote for your deal or a revised deal you can agree with my party.

"I will help you get it over the line to prevent a disastrous no deal exit. But I can only vote for your deal - or any deal - if you let the people have a vote on it too."

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Hundreds of thousands will set off from Park Lane to Parliament Square tomorrow, to demand a second Brexit referendum.

The event is being organised by the People's Vote campaign, who organised a similar demo in October at which 700,000 people are thought to have turned out.

The rally, which will be attended by politicians, celebrities and campaigners will take place just six days before the UK is due to leave the EU.