The EU’s chief Brexit negotiator and his UK counterpart will have a private dinner in Downing Street on Tuesday evening, where fish will be on the menu.

Michel Barnier and David Frost will kick off the latest round of trade-deal talks by dining on chargrilled asparagus, followed by a fillet of halibut and then a terrine of summer fruits at Number 10.

Major stumbling blocks on the road to a deal include the “level playing field” – conditions Brussels demands to ensure fair competition by keeping the UK closely tied to EU standards on workers’ rights, the environment and state subsidies – and fishing rights.

Mr Barnier said the EU is “doing everything to succeed” in reaching an agreement “but not at any price”.

He posted a message on Twitter showing himself and aides wearing face masks on the train to London.

“We are engaging constructively and I look forward to equivalent engagement from the UK this week,” he said.

The Prime Minister’s official spokesman said that while the talks are “informal”, discussions are likely to “cover everything from what the EU calls the level playing field through to governance structures”.

No ministers will be present at the dinner but “one or two” officials from each side may attend. Downing Street said social distancing rules would be obeyed.

The two negotiators will be joined by their teams for further talks on Wednesday.

Meanwhile on Tuesday, the PM spoke to German chancellor Angela Merkel and told her that the UK “would be ready” to leave the transition period at the end of the year without a trade deal with the EU if one cannot be brokered, according to Downing Street.

Last week, discussions between the two sides on a post-Brexit trade deal broke up early with “significant differences” remaining.

It had been hoped that the face-to-face meetings – agreed following a high-level conference call last month between Boris Johnson and European Commission president Ursula von der Leyen – would inject new momentum into the process.

The Prime Minister has been adamant that he will not allow the discussions to drag on into the autumn, arguing that British businesses and citizens need certainty on the way forward before then.

If the two sides are unable to reach a deal by the end of the current Brexit transition period at the end of the year, it will mean Britain leaving the single market and the customs union without any agreement on future access.