Andrew Adonis’s resignation means the fight against Brexit may be turning into a campaign to rejoin the EU

The former minister’s tirade against Theresa May could mark the turning point in the campaign to stay in the European Union

Andrew Adonis is one of the most remarkable ministers of postwar Britain. Apart from prime ministers and chancellors, few ministers leave a mark. James Callaghan as transport minister introduced zebra crossings – the first trial ones were blue and yellow stripes – in 1949, although he was later Chancellor and Prime Minister. Barbara Castle as Minister for Transport introduced the breathalyser.

Adonis was a transport minister too, and leaves the High Speed 2 rail link, planned to open in 2025, as his monument. But he was also an education minister in Tony Blair’s government, creating academy schools, which have helped improve the life chances of hundreds of thousands of people. And he created Teach First.

Naturally, his achievements are controversial, but as a force for change Adonis has had no equal. He continued to drive ambitious and creative ideas as chair of the National Infrastructure Commission, to which George Osborne appointed him in 2015, because he wanted the Commission to have the “bipartisan authority to generate a national consensus over long-term thinking”. So much for that high-sounding idea.

Adonis’s impact is all the more extraordinary because, as those who disagree with him are quick to point out, the only thing to which he has ever been elected is Oxford City Council (he was a Social Democrat and then a Liberal Democrat councillor, 1987-91). His impact on national life has been achieved as a policy adviser at 10 Downing Street from 1997, as a minister in the House of Lords 2005-10, and as head of Osborne’s quango.

In each of those roles, of course, he did what elected leaders wanted him to do, but now that run has come to an end. Predictably, the suggestion from No 10 is that the Prime Minister was about to get rid of him anyway, just as Alan Milburn resigned before the Government had the chance to fail to renew his term as chair of the Social Mobility Commission. Milburn was another consequential minister in the Blair government, recruited by David Cameron and Osborne to provide a veneer of cross-party reasonableness.

Theresa May tends not to bother even with the veneer. She sacked Michael Heseltine as a government adviser in March because he defied the Conservative whip in the Lords to vote against invoking Article 50. But she was curiously passive about Adonis, allowing him to campaign noisily against Brexit while retaining his official post – and hence allowing him to strike first with his incendiary resignation letter on Friday.

In the letter, Adonis comes out with fists flying. He accuses May of betraying the national interest in her approach to Brexit, which is a little odd, since her direction – excluding Britain from the EU single market and the free movement of people – has been clear since before she became Prime Minister 18 months ago. But he says he had to resign because the EU (Withdrawal) Bill, “the worst legislation of my lifetime”, will soon come before the House of Lords, “and I feel duty bound to oppose it relentlessly from the Labour benches”.

He calls Brexit “a dangerous populist and nationalist spasm worthy of Donald Trump”, and accuses her of “becoming the voice of Ukip”. Note that he picks up on the theme of populism, the subject of a paper this week from Tony Blair’s Institute for Global Change, which traces the rise in European and US politics of nationalist leaders stoking hostility to elites, minorities and immigrants.

Adonis appears to be pursuing a twin-track tactic in the fight against Brexit. You might think his resignation and heated rhetoric would be counterproductive in seeking to persuade soft Leave voters that they should think again. But I suspect that he, and Blair, along with Heseltine and Kenneth Clarke and the other ultra-Remainers, are trying to create space for moderate doubters to emerge. They know that public opinion on Brexit is likely to shift only if prominent Leavers say they are having second thoughts, and they hope that, as outriders, their melodramatic warnings will make that easier.

It seems a forlorn hope to me, and it seems Adonis also knows that the chances of averting Brexit are small. In one of the significant passages in his resignation letter, he tells May: “Taking us back into Europe will become the mission of our children’s generation, who will marvel at your wanton destruction.”

Admittedly, this comes after an “if” – if May’s version of Brexit succeeds in putting up “barriers between people and trade even within Ireland”, then the next generation would try to rejoin the EU. But the prospect of a different kind of Brexit – the Norway option of being in the single market without a say over it – seems remote. The only way it could happen would be if the EU27 allow the UK to restrict free movement, which seems even less likely.

It seems that Adonis accepts that Brexit cannot be stopped or changed, and is preparing the ground for the longer struggle. Far from being a call to arms against Brexit, it could be that Adonis’s resignation marks the moment the ultra-Remainers admit defeat in this war and start to prepare to fight the next one.

It could be that 2018 will be the year in which opposition to Brexit transforms into the beginnings of the campaign to rejoin the EU after we have left.