Brexit negotiations have resumed in Brussels in an attempt to break the deadlock over four key issues: fisheries, fair competition in trade, governance and security. Talks started on Monday with a two-hour, face-to-face meeting between David Frost, the chief UK negotiator, and the EU’s Michel Barnier, the first since the Covid-19 outbreak halted talks in March. As Frost and his team of a dozen-plus negotiators headed to Brussels by train on Sunday, it was being revealed that Boris Johnson had given him a new role (and a peerage) as his national security adviser. How does Frost’s appointment affect Brexit talks? The timing of Frost’s appointment could not have been more pointed. Although the vacancy has arisen because of the resignation of the cabinet secretary, Sir Mark Sedwill, on Sunday night, giving the post to someone who is leading arguably the most important international talks since the Iraq war in 2003 sends a strong message to Brussels that the UK is prepared to walk away if a deal cannot be struck in summer talks. Frost is due to take up his new role in September and this cuts perilously short the time in which to seal the comprehensive and ambitious deal Johnson claims he wants before the end of the Brexit transition period. The prime minister’s spokesman said on Monday Frost would not be replaced as chief negotiator but said he would continue to lead the negotiating team even after his appointment as security adviser. Many will be concerned that such double-jobbing will compromise his capacity for his Brexit role but he has the full support of Johnson, who describes him as a “serious diplomat, policy thinker and negotiator”. What is the remaining timetable for Brexit talks? This week is one of six rounds of week-long talks, five between now and the end of July, with the final round scheduled for 17 August. On the agenda are governance, fisheries, level playing field, trade in goods, trade in services, criminal law and judicial cooperation, energy and transport, participation in EU programmes such as science research, and continued mobility of social benefits for EU citizens in the UK and British citizens in the EU. What are the chances of a deal? Both sides have expressed the real prospect of no deal. Johnson said this month he wanted to see an outline of a deal emerge from the July talks while the European parliament president, David Sassoli, last week said the EU had been left concerned at the end of a video conference with Johnson two weeks ago over the lack of “enthusiasm” the prime minister seemed to have to find common ground on the most contentious issues. What are the main issues? The two sides remain fundamentally divided on the four key issues stated above but notably on the role of the European court of justice in dispute resolution and governance. Frost has said there can be “no halfway house” on the role of the ECJ or other EU institutions. The Cambridge law professor Catherine Barnard, an expert on EU law, recently told a government select committee it was “quite difficult to find a really good landing zone” here and not just because the UK objects to the ECJ. The problem is that what both sides will be striving to adjudicate are breaches of an international treaty rather than company contracts, meaning disputes over the Brexit deal “will be state to state rather than private party to private party”, she said. What about security and defence? Given that Frost’s new job will be to advise the government on this issue, it is ironic that this is the one topic the UK has decided not to engage in any negotiations although it can be argued that defence can be driven by events such as war and other platforms such as Nato. However, concerns have been raised over weaker security ties, on extradition, and on Britain’s desire to have continued access to real-time passenger records for counter-terror responses without conditions. Is there any hope? Yes. It is hoped that five weeks of face-to-face meetings might yield results as they allow more nuanced discussions in informal meeting in corridors and over dinners. This week’s meeting is restricted to about 16 people from each side compared with 100 in previous rounds, allowing for further frank discussion.