It would be absurd to claim to see a silver lining behind every Donald Trump cloud. Those clouds are too many, too dark and too dangerous. All the same, viewed from a domestic political perspective, there is a clear emerging British upside to Trump’s efforts at crashing the post-cold war order. It might even get a boost from Thursday’s Washington visit by Keir Starmer.

In July 2024, when Starmer became prime minister, Labour was rigidly on the defensive about Europe. Brexit was seen as an electorally unstable issue for a party whose priority was to reconnect with leave voters. Everything about Europe was thus sidelined during the election. Only vague generalities were permitted. The only foreign leaders pictured in the party manifesto were Ukraine’s Volodymyr Zelenskyy and Canada’s Justin Trudeau.

Since July, Labour in government has continued to tread warily. Starmer’s personal goodwill towards Europe was clear in international meetings, especially bilaterals. But he remained circumspect and nervous about re-engaging on policy specifics, especially with the EU itself. For instance, a report last week that the UK would agree with the EU on youth mobility visas was quickly knocked down by the government.

Downing Street’s response here was explicit. Such a scheme, even though only applying to 18- to 30-year-olds, restricted to a three-year limit and subject to an annual numbers cap, would be depicted as a resumption of pre-Brexit freedom of movement. It was not going to happen, said No 10. The reason is simple. Starmer is determined to prevent any replay of the Brexit years from entering the domestic political arena. The Liberal Democrat leader Ed Davey’s recent proposal for Britain to rejoin the European customs union also got a similarly immediate brush-off.

Importantly, the Conservative opposition is also cautious about Europe, although for quite different reasons. Brexit still remains part of the Tory party’s creed. But even some Tory true believers can see there’s a problem. Brexit is synonymous in the public mind with the chaos of the Johnson, Truss and Sunak years, which led to the party’s worst modern election defeat last year. Nor has Brexit delivered any of the advantages promised in 2016. The Tories are therefore content with the standoff too. Even Reform UK says little about Brexit. Only the Lib Dems and the Scottish nationalists feel unfettered by the issue.

The politics of the UK-Europe relationship might have stayed quietly frozen there for the next two or three years, despite Trump’s return. That was, after all, the original Labour government plan. So much has happened in Washington so quickly that it is perhaps hard to remember that, just after the 20 January inauguration, the UK was wholly focused on trying to embrace Trump as much as practicable, as well as on keeping out of the developing US-EU tariff battle.

That changed for ever with Trump’s volte-face on the Russia-Ukraine war. By embracing Russia, and trashing Ukraine and Zelenskyy, Trump exposed the true scale of the security threat to Ukraine and Europe that would result from a deal between him and Vladimir Putin. JD Vance underlined the realities in Munich shortly after. As a result, Trump drove Britain and Europe closer together far sooner than might have happened if Kamala Harris had become US president. Starmer now talks almost daily with Zelenskyy and, just as importantly, with Emmanuel Macron.

This change is the product of necessity. It has been brought on by Trump’s recklessness. But it has a positive side. It forces Starmer to engage far more actively with Europe on defence and security. This is desirable all round. One consequence was Tuesday’s defence spending hike announcement. But this may be only the start.

A further paradox is that Trump has also forced Kemi Badenoch and the Tory party to support Starmer’s more Europe-oriented response. Having backed Ukraine so passionately under Boris Johnson from 2022, anything else would discredit the Conservatives further. Remarkably, the Tories have almost nothing to say about a shift that would have been anathema in Johnson’s day. Even Nigel Farage, though less heavily politically invested in support for Ukraine and Zelenskyy, has had to join the slipstream.

All of which has gifted Starmer a new and previously closed space in British politics. Building up Europe’s defence effort is suddenly the patriotic course. In the past, it would have been depicted as divisive, anti-American and anti-Nato. Instead, with the US threatening to turn its back on Ukraine, Europe and even Nato, it is Trump who is now divisive. There is an echo here of modern Britain’s Churchillian mythology, and of the words uttered by a defiant British soldier who raises his fist to the gathering storm in David Low’s iconic 1940 cartoon: “Very well, alone.”

Now, though, it is all Europe, not Britain, that stands alone. Trump deserves two sorts of credit for this amid all the justified condemnation. First, because all of Europe should have seen and acted earlier on the security need anyway – not exactly difficult after Putin’s seizure of Crimea and Trump’s first term. Second, because it pushes Britain closer to Europe more generally. This increases the possibility for other forms of European joint action, not just in defence, that will sometimes be based on nation states and not exclusively on the disturbingly unwieldy EU.

Last weekend’s German election is potentially pivotal here. The likely German chancellor, Friedrich Merz, has long been open both to stronger German defence and, like Macron, to what is known in EU-speak as “variable geometry” relationships. This is where the priority for Europe’s future lies, not just for Britain. Whether these things will happen, and whether they will be sustained by the Merz-Starmer generation of leaders, are different questions altogether. But Trump has given Europe a chance. There is a gleam in the dark.

• Martin Kettle is a Guardian columnist