The Taoiseach’s lunch with Boris Johnson at Chequers on Friday comes amid tension between Dublin and London over the Northern Ireland protocol and the legacy of the Troubles.
It also coincides with the election of a new leader of the Democratic Unionist Party (DUP) in which both candidates have promised to suspend North-South contacts until the protocol is changed or abolished.
Mr Johnson this week stepped back from a proposal to block all prosecutions for alleged crimes by British soldiers during the Troubles, apart from war crimes, genocide and torture.
The proposed amnesty, which would also apply to loyalist and republican paramilitaries, was not mentioned as part of a legacy bill in the queen’s speech on Tuesday.
The prime minister remains under pressure from Conservative backbenchers to protect former soldiers from prosecution but the fierce backlash to the leaked amnesty plan from Belfast and Dublin has stayed his hand for now.
Mr Johnson’s clumsy apology to the victims of the Ballymurphy shootings, which had to be extracted over a number of days, has further weakened his position if he is seeking the Taoiseach’s support for a Troubles amnesty.
The prime minister wants the Taoiseach’s help as Britain seeks to persuade the European Commission to introduce further flexibility in the operation of the protocol.
David Frost’s visit to the North did nothing to convince the EU of Britain’s good faith and his reported meeting with the Loyalist Communities Council (LCC), which includes paramilitary representatives, was seen as encouraging their opposition to the protocol.
Marching season
Lord Frost and Mr Johnson are likely to warn the Taoiseach over lunch that the North’s marching season creates a deadline for reaching decisions that will ease anger over the protocol. The British side claims the EU is now a player in Northern Ireland and shares responsibility for stability there.
Despite Lord Frost’s rhetoric, some progress has been made on efforts to ease the impact of the protocol.
Sources close to Lord Frost expect some additional issues to be resolved by next month but some major difficulties are likely to remain.
Britain has ruled out a veterinary agreement based on dynamic alignment with EU rules, which would eliminate the need for many of the most cumbersome checks.
London has also rejected a European suggestion that Britain could temporarily align with EU food safety rules but could end the arrangement if necessary as part of a trade deal with, for example, the United States.
The British side are pushing a “data-driven” approach that would determine the level of checks on particular goods based on evidence about how likely they are to cross the Border.
The EU side complains that Britain has yet to fulfil its obligation to give European officials access to databases about goods movements.
Mr Johnson will hope to persuade the Taoiseach to act as Britain’s advocate in Europe on the protocol but that is a proposal Mr Martin is likely to scrutinise with some care.