One key obstacle remaining is the Irish border issue - on how to keep the new EU-UK land border with Northern Ireland open as it becomes the EU's new external border on the island of Ireland.

"Clearly Number 10 are negotiating a "backstop" that makes the United Kingdom a permanent European Union colony", former foreign minister Boris Johnson warned on Wednesday.

Under pressure from all sides, Theresa May told journalists at Downing Street reception that talks on the key issue of the Irish border were likely to continue until November, while cabinet ministers who met with May on Thursday evening were cited by the Financial Times as saying the border issue was close to being settled.

Commenting on the Irish backstop, Barnier said the EU's plan to keep Northern Ireland in the Single Market and customs union would help keep the border invisible - a goal of both sets of negotiators.

By withdrawing its support, the DUP could make it hard for May to pass legislation through parliament, including the budget which will be voted on later this month.

Sammy Wilson, the DUP's Brexit spokesman, warned the PM was pursuing "the road to parliamentary defeat" because his party would vote against any deal that included the proposed backstop, branded a "sell-out".

"They [the EU] said they think this is an wonderful deal you are getting, something nobody else in the world has even been offered", said Seamus Leheny, the director of policy at the Freight Transport Association of Northern Ireland, who was at the meeting.

I caught up with her in Brussels and asked her if she thought the Prime Minister had got the message.

It will follow another Whitehall meeting of the Joint Ministerial Committee, which will be attended by Mr Lidington and his colleagues Dominic Raab, the Brexit Secretary, and David Mundell, the Scottish Secretary. Can all three ever be satisfied with the terms of a Brexit deal?

Last night, it was suggested a group of up to 30 Tory Remainers were considering forming a rival campaign to fight Jacob Rees-Mogg's European Research Group of Eurosceptics with the aim of voting down Mrs May's Brexit deal because of fears it would wreck the economy.

He also stressed the EU's insistence that Britain must accept possible checks on goods moving between its mainland and its province of Northern Ireland, saying Brexit will trigger the need for customs, value-added tax and compliance checks with European Union standards.

Labour demands that Britain retain "the exact same" perks it now has within the EU's customs union and single market - something May's so-called Chequers plan does not meet and which the EU rules out since London chose to leave both.

"It was a warning: 'Don't take us for granted, we're in an agreement with you, but it's a two-sided agreement. I sympathize with her on that but there is no answer to that problem", he told the audience.