David Lammy will be the first Labour foreign secretary succeeding a Conservative government since Robin Cook in 1997, if his party triumphs in the general election. On his arrival in office, Cook’s first two acts were to expand the Foreign Office newspaper subscription list to include the Racing Post, and, perhaps more momentously, give an interview to the Observer hailing “an end to xenophobia”.

Lammy will be less bothered about racing tips, but he is tempted to send a broadly similar signal to Cook’s about how the UK under Labour is going to reconnect with the world.

He wants to signal three big resets: with Europe, on the climate crisis and with the global south. A planned visit to India in the first month will give a platform for the latter two.

It is said that foreign policy occupies 5% of the time of an opposition party, but 50% of the time once that party reaches government. Labour, barring an electoral meteorite, is readying itself for that sudden adjustment. For months, it has been holding meetings both with Foreign Office officials and the political team around the foreign secretary, David Cameron.

It is shaping up to be a daunting transition, not least because two major wars are under way, both with the potential to expand their geographical boundaries at any moment. Still worse, Lammy’s natural allies in the Democrats are in turmoil in the US. The whole context of his foreign secretaryship, including relations with China, may turn on the US presidential election, for which all he can do, as he has done, is ensure that his lines to the Republicans remain open.

One of Lammy’s first tasks will be an internal address to the diplomatic corps in the ornate Durbar Court, once part of the India Office, and restored in the 1980s. Diplomats will welcome him in the hope that change in this case also means stability. After eight foreign secretaries since 2014, continuity, and the knowledge that the foreign secretary enjoys the prime minister’s confidence, is what the diplomats crave. But they will also be trying to judge what Lammy’s phrases “progressive realism”, the “end of post-colonialism” and “dealing with the world as it is”, mean in practice. Lammy has tried to dampen expectations by saying the challenge will be how to operate according to Labour values in a world that often doesn’t share them.

Judging by a recent Chatham House seminar led by London-based ambassadors, European diplomats also hope that the UK under Labour will be a source of stability, a near reversal of the past few years in which Europe has looked across the Channel to a country in chaos.

The broad contours of the landscape facing the relatively small incoming Labour foreign team have been known for a few months, but as the moment of touchdown has neared, the shape of the key landmarks has sharpened.

Two immediate diplomatic set pieces – a Nato summit in Washington starting on 9 July and a European Political Community conference hosted by the UK on 18 July and attended by 47 leaders inside and outside the EU – will provide Keir Starmer with a crash course in multilateralism. First impressions matter.

Both events will have a strong Ukraine focus. The forms of words about Ukraine’s future membership of Nato – including the staging posts – are already broadly agreed. Labour will also inherit the previous government’s enthusiasm for Nato coordinating weapon provision to Ukraine. Labour has ideas of its own on how to downgrade Russian weapons production.

At Blenheim, as host, Starmer’s hope is to convince European leaders that reset will be real. Starmer wants to show he welcomes Emmanuel Macron’s fledgling new forum for European cooperation, and to urge others to shelve their doubts. But that requires some tangible outcomes. Europe is being pulled in different directions on Ukraine with some wanting to go deeper. Many, not just Serbia and Hungary – ideologically aligned with Russia, or eager to trade – are looking for a way out.

The meeting will also come as one of the pillars of Europe’s foreign policy is tottering. All eyes will be on the French, especially if the second round of national assembly elections on 7 July mean Macron is into the second week of political deadlock inside the assembly or facing cohabitation with a potential new far-right prime minister in Jordan Bardella.

In the French constitution, Macron remains sovereign in foreign policy, but Marine Le Pen has pointedly warned that the assembly holds the purse strings, and the president’s title of commander of the forces is, in her view, honorary.

The former UK national security adviser Peter Ricketts said: “Macron may have put France on collision course with chaos. If there is no workable majority, France would be in completely uncharted territory.” He does not rule out Macron’s seismic resignation as president in the interests of the Fifth Republic’s survival.

The French crisis is ill-timed for Labour since Anglo-French defence cooperation is the building block of Labour’s proposed security pact with the EU, a pact that is difficult to negotiate if Europe is divided on issues such as Ukraine or integration of the European defence market.

The EPC feels like an event to survive, rather than launch anything substantive. Lammy’s advisers said talks on a security pact with the EU would take time to prepare.

Much of this high diplomacy may seem abstract to Labour party members. Their eyes will be elsewhere. Indeed at noon on Saturday, 36 hours after the polls close, Labour activists and pro-Palestinian groups will gather yet again in central London to demonstrate about Gaza, but this time their demands will be directed at a Labour government.

However large Starmer’s majority, and however loyal the Muslim vote proves, his backbenchers will be asking what is going to change in the UK’s approach to what many, according to Ben Jamal the chief executive of the Palestine Solidarity Campaign, regard as the great moral issue of their time.

Jamal said: “It is unlikely by polling day that there is going to be any ceasefire in place, partly because no meaningful leverage was placed on Benjamin Netanyahu to accept a permanent ceasefire, so the barrage of pressure on Labour is going to be immediate.

“There will be tens of thousands on the streets of central London on Saturday, the day Keir Starmer moves into Downing Street, and people will want answers about arms sales. How long is it going to take for them to read the legal advice that is self-evidently going to have found there is a serious risk UK arms are being used to breach humanitarian law? It is going to be a test of how far they are going to go to support international law. They cannot just say we don’t know if international law is being breached. They will have advice, and they have said it should be published. They are in charge now.”

Labour will resume funding of the UN Palestinian relief works agency Unrwa, but Starmer would be reluctant in one of his first acts to antagonise Israel’s supporters inside the Labour party. Netanyahu’s anger directed at Joe Biden for slowing US arms supplies is a clear warning that any British embargo on arms sales will be portrayed as a betrayal of Israel.

Nor will any of Lammy’s internal party management issues be made any easier by the darkening wider Middle East context. For months, the concern has been that the conflict in Gaza will eventually turn into a full-scale conflict with Hezbollah in Lebanon, and that in turn raises further questions about Iran.

Oppositions, of course, can only interpret the world. Now Lammy is about to find out whether he can help change it.