Video report by ITV News Political Correspondent Paul Brand

ITV News has been granted rare access to the office of the Conservative Chief Whip, following his progress in recent weeks as he tries to win round sceptical members of the Prime Minister's own party.

He also agreed to an interview with political correspondent Paul Brand - an unusual move for the man who usually keeps the workings of his team a closely-guarded secret.

Tense negotiations, heated debates and political wranglings.

It could well be the tagline for House of Cards.

But this is no drama - it's the reality of life as the government's Chief Whip, Julian Smith, took the highly unusual step of inviting ITV News behind the scenes as he and and the Prime Minster fight to get her Brexit deal approved.

"We've certainly got our work cut out for us over the next couple of weeks," Mr Smith acknowledged, sitting down with his team at the very beginning of our visit.

"But I think we've got a plan in terms of how we're going to engage with colleagues."

We filmed that plan in action, as the Chief Whip met those who are vocally opposed to Theresa May's deal.

The agreement Mrs May has negotiated with Brussels will go before the Commons on Tuesday, with around 100 Conservative MPs - plus their partners in the DUP - still insisting they'll vote against it.

In one heated exchange we captured, the Chief Whip pressed the Brexit-supporting MP Philip Davies MP on his concerns about the Northern Irish backstop.

He stressed: "We have to get your support for this deal... how do we resolve this?"

Mr Davies replied: "I'm not sure that you can.

"I don't really see any alternative other than the Prime Minister going back to the EU and saying look we need something in here, whether it's a time-limit, there's got to be something in there."

This is the people against Parliament, and the government should be on the side of the people. Philip Davies MP

He said his main concern was the Northern Irish backstop.

"This is all about taking back control, and we're going to be in something that we can't control," he said.

"I always agreed with the Prime Minister that no deal is better than a bad deal. And to my mind, this is a bad deal."

The Chief Whip meets with his fellow Whips ahead of Tuesday's vote. Credit: ITV News

The Chief Whip described how he was using a colour-coded spreadsheet to track each Conservative MP, and their likelihood of voting for the Brexit plan - along with the concerns each of them had.

He said this vote was the most important one Parliament faced, other than going to war.

"It's a 24/7 job at the moment - I have to say I sleep very little and Brexit is always on my mind," he said.

But in his final interview with ITV News today, Mr Smith admitted it was an "uphill challenge" to get MPs, such as Mr Davies, behind the Prime Minister's deal.

Paul Brand explains where we are on the issue of a second referendum

But he told ITV News that there would be no delay to Tuesday's vote, after speculation it may be postponed for fear of defeat - stating three times: "The meaningful vote is happening on Tuesday."

He also said there was "no plan" if Mrs May loses.

"We are changing minds, and I think we're making sure that we are making the arguments across detailed policy issues that colleagues have," he said.

"There is no plan for a vote loss. This is the deal. This deal that we're putting on the table is the deal that we need to get through Parliament."

However, he admitted that the government was having to look at new ways to win over MPs on the Northern Irish backstop, saying Parliament would be "sovereign" when it came to deciding whether or not to enter such an agreement.