Now, a transitional period is set to last from March 2019 to the end of December 2020.
The agreement on the 21-month period, which Theresa May promised in order to provide certainty to businesses, is a huge economic boost and led to a surge in the pound. Under the deal, the United Kingdom could pay over €37bn until 2064, according to figures released last week by the UK's Office for Budget Responsibility.
He also welcomed wording that gives Britain some say in European Union policy during the transition, notably on fishing quotas, and an ability to refuse to implement things it did not agree with - some of his Conservative party allies have complained that the transition deal would leave Britain a "vassal state" of the EU.
The agreement allows for a almost two-year transition period, ending on December 31, 2020.
Britain and the European Union on Monday reached a landmark deal on a transition phase that will see London follow the bloc's rules for almost two years after the Brexit divorce. There are still key issues that need to be resolved and none more so than the vexed question of the Northern Ireland border, which will take some unpicking.
"As far as financial services are concerned, the aim must be a revised and improved equivalence mechanism that allows appropriate access to the financial services markets while preserving financial stability, the integrity of the single market and the decision-making autonomy in the EU", says the draft.
The U.K. has agreed in principle that a "backstop" solution to the Irish border problem will be included in the final withdrawal agreement, giving Dublin the legal guarantee that there will be no return to the hard border of the past.
Any single member can veto the UK's future relationship with the European Union and derail the process, meaning no deal is agreed before 2020.
The EU argues Northern Ireland must obey the bloc's regulations if a "soft border" is to remain, but the British government and Northern Ireland politicians will have none of this.
"It remains our intention to achieve a partnership that is so close as to not require specific measures", Davis said on Monday, insisting on a solution "that is acceptable to both sides".
It is why EU's deal with Canada (Ceta) took seven years to negotiate and was nearly derailed at the final stage of the ratification process by the Belgian region of Wallonia.
The UK and European Union hope that if a transition deal is agreed, then negotiations can focus on what sort of permanent future relationship the two sides will have - with the aim of a deal being agreed in the autumn to allow time for European Union member states and the UK Parliament to ratify it before Brexit next March.
Davis agreed with Barnier that Monday's agreement was "decisive" and increased the odds on finding an orderly deal to avoid Europe's second-biggest economy simply crashing out of the bloc in just over a year.
"Ireland first", European Council president Donald Tusk warned earlier this month.
Mr Wick said that the government had "thrown the fishing industry under the Brexit bus" and that Northern Ireland fishing businesses could be under threat.