On Tuesday evening MPs will exercise their meaningful vote to support or reject Theresa May's EU-endorsed Brexit deal.
A majority are expected to snub the prime minister's withdrawal agreement in a bid to force more negotiations with Brussels.
But where do MPs actually go to vote before the Ayes and Nos are declared in the House of Commons?
Let ITV News Political Correspondent Carl Dinnen walk you through their literal steps - from the Despatch Box and back again - as he gains rare access to the corridors of power ahead of the vote.
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