On 2 March 2020, nearly four years after the referendum, Michel Barnier and David Frost kicked off the talks in Brussels on a new partnership. They sat opposite one another at a large oval table in the Robert Schuman meeting room of the Berlaymont, with around 20 collaborators on each side. Frost and Barnier did not know each other well. Frost had mostly dealt with Barnier's collaborators for the 2019 talks on Northern Ireland and the political declaration, when Barnier was mostly in touch with the Brexit Secretary Steve Barclay. For 2020, Johnson did not appoint a cabinet member for the negotiations. Michael Gove took political responsibility in the Commons for what Johnson's special advisor was doing and Frost himself took on gradually a more public persona via Twitter and speeches. EU negotiators regarded Frost as aloof, not always truly engaging in conversations or applying flexibility to search for common ground, although his repetition of known UK positions was also a way to test the EU's resolve. At university, Frost had studied medieval French but his fluency in French did not bring his relationship with Barnier beyond the professional and functional remit. Both men would try to create a warmer atmosphere by meeting regularly for lunch. Barnier respected Frost, even though he disagreed with his worldview, and he appreciated Frost's gesture of inviting him for dinner in de Gaulle's wartime office in London, but there never seemed to be much chemistry between them. After December 2020, they lost touch. Of the four negotiators with whom Barnier worked, only David Davis sent him a message to congratulate him on the deal. David Frost wished him well when he left the Commission to return to French politics a few months later.

British journalists often referred to the negotiations as the “trade talks with the EU”. Foreign and security policy, as well as police and judicial cooperation, featured less in political coverage but they were equally crucial components of the agreement and important for the structure of a new European security architecture. As with trade, there was a palpable difference on these matters between Theresa May and Boris Johnson.