Sir Keir Starmer’s inbox is packed to bursting point, and that was reflected in this week’s King’s Speech. From overhauling the planning system and setting up both Great British Energy and a National Wealth Fund to invest in infrastructure and green industry, to renationalising passenger rail services and establishing new employment rights, the new Labour government is hitting the ground running.

Sir Keir and his government have quite enough to deal with on the domestic front, but the diplomatic demands on him and his Foreign and Defence Secretaries are just as substantial. War continues to rage in Europe as we plunge deeper into geopolitical transition and instability globally. And it looks increasingly likely that that creaking inbox will explode after November and Donald Trump’s election to a second term as President of the United States.

Now, let’s be clear about something. The polls before last Saturday’s events suggested that President Trump and President Biden are neck-and-neck, and so do the polls released since. But most polling conducted in the swing states that will decide the outcome of the election showed Trump ahead before his attempted assassination and continues to show him ahead. If they are accurate and do not change by November, he will win the election.

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What has become increasingly clear, and thoroughly crystalised this week as the Republican Party gathered for their convention to officially name President Trump their nominee, is that a second Trump presidency will be a pure, America First presidency from day one. And that will present the new Prime Minister and his Government with substantial headaches.

The first Trump presidency, as chaotic and malign as it may have been, and ending as it did with insurrection on January 6, 2021, was one in which the worst instincts of President Trump and his coterie of far-right political warriors were substantially restrained by more moderate heads in the Republican Party, political appointees foisted upon him by those Republicans, and by the professional American civil service. The Pentagon and Defence Secretary James Mattis were a case in point, pushing back on President Trump’s more isolationist tendencies and, in multiple instances, outright refusing to carry out his instructions.

But by the end, they were gone and sycophants and true believers increasingly surrounded President Trump. Since his defeat in 2020, the Republican Party has become even more President Trump’s party. High-profile opponents within the Republican Party, like Liz Cheney, are gone. President Trump’s daughter-in-law now runs the Republican Party’s professional apparatus. Even his staunchest opponent during the Republican primaries, Nikki Haley, has pledged her “strong endorsement” of the former president. And his control over the Republican Party was made complete by his attempted assassination. President Trump is now not just the Republican nominee, but a living martyr to the America First ideology that permeates that party and its policy platform.

President Trump’s appointment of Senator James David Vance as his Vice-Presidential nominee is the latest indicator that a second Trump presidency will be untethered from the restraining forces of the American political establishment. The author of Hillbilly Elegy, who hails from a working-class Ohio community ravaged by deindustrialisation, once characterised President Trump as “cultural heroin”, a reference to the opioid epidemic that has swept working-class America since the 1990s, intensifying after the financial crash, and has come to see various prescription opioids nicknamed "hillbilly heroin". However, Senator Vance is an economic populist in the Trump mould and is today an almost sycophantic supporter of the former President and his policy platform.

A Trump-Vance administration would be staffed by the same Trump acolytes who played central roles in drafting the Heritage Foundation’s "Project 2025", which calls for reclassifying tens of thousands of federal civil servants as political appointees to replace them with Trump loyalists: a goal aligned with President Trump’s stated aim of clearing out “America-Last globalists in the Deep State”.

Having replaced layers of the American civil service with loyalists, a renewed Trump presidency will pursue his "Agenda 47" policy platform. His plan to end the war in Ukraine on day one of his presidency would favour Putin’s Russia and signal both the collapse of America’s resolve to guarantee European security and a return to a Europe in which there is a place for expansionism.

Even Nikki Haley has pledge her support for Donald TrumpEven Nikki Haley has pledge her support for Donald Trump (Image: AP)

These agendas favour a radical re-orientation of Nato, going as far as instituting a "two-tier" system in which the US would refuse to engage militarily to defend Nato allies that are invaded by a foreign power if they have not hit the target of spending 2% of their GDP of defence. Any prevarication over the universal applicability of the mutual defence commitments that form the basis of Nato’s deterrence of foreign adversaries could fatally undermine the alliance.

And in economic affairs, they call for universal baseline tariffs on foreign goods that would hit the UK’s more than £300 billion of exports to the US, accounting for 17.6% of our trade.

A second Trump Presidency, unrestrained by the forces that kept his first administration in check, would pose a potentially existential crisis to the Western alliance and the UK in particular - more isolated, as we are, from our European partners than we have been in decades.

The UK Government is aware of these risks - there is a reason they are already engaged with President Trump and his team. If he is elected to a second term, the transition period will see a flurry of intense diplomatic activity as the UK and other Nato allies attempt to shape the foreign policy of the incoming administration and take the sting out of its tail.

It's fine to hope for the best, but we must be prepared for the worst. In a world in which the US is increasingly isolationist, closer relationships with our European allies will be even more critical to the UK economy and national security.

Yesterday’s meeting of the European Political Community, hosted by the Prime Minister at Blenheim Palace, marked the start of a reset of our relationship with Europe – but it is only a start. Preparing for a Trump presidency necessitates planning to forge a European economic and security architecture that can withstand even partial American withdrawal, and the UK must take a leading role in that process. A closer relationship with Europe is not a "nice-to-have’" it is an economic and national security imperative.