What could be the final act in the long-running drama of Julian Assange’s legal battles has opened at the High Court in London. The two-day hearing is considering the Wikileaks founder’s appeal for a review of his extradition to the United States, which was given the go-ahead two years ago and approved by the then-Home Secretary, Priti Patel.

The US had applied for his extradition on 17 counts of espionage and one of computer misuse in connection with the publication of a large trove of classified material, which included sensitive diplomatic cables and video recordings of US military operations in Afghanistan and Iraq. Among then, most notoriously, was quite shocking cockpit footage showing the killing of Iraqi civilians in Baghdad, including a Reuters photographer and his driver.

The case has gone to and fro between the courts. Extradition was initially refused on the grounds that the likely conditions of his detention in the US could precipitate his suicide, then approved after the US appealed and offered certain guarantees about his treatment. This week’s hearing effectively appeals that decision, with counsel for Assange arguing for a review of the previous ruling.

If Assange wins, the whole case for his extradition could be reopened, or the US could drop its case and Assange could taste freedom for the first time in more than a decade. If he loses, he could find himself on a plane to the United States sooner rather than later, although there could also be an appeal to the European Court of Human Rights in Strasbourg. That, however, would depend on the ECHR agreeing to hear the case and the UK blocking any extradition flight pending the judgment – neither of which would be a foregone conclusion.

As ever with court hearings relating to Julian Assange, the theatre began early outside the court, with banners, speeches and chants by his loyal supporters, including his one-time lawyer and now wife, Stella, who see his case, at root, as a fundamental test of the right to free speech in the UK. As ever, too, the players outside the court were a bizarre mix of not always popular home-grown activists, such as Jeremy Corbyn MP and Russell Brand, and passionate politicians and activists from around the world, especially from countries where the absence of free speech and the rule of law has been a reality within living memory.

Inside, it was soon apparent that, although Stella Assange had said her husband hoped to attend in person rather than by video-link, he was not there in either capacity. His years of confinement – seven at the Ecuadorian embassy near Harrods in London, and now five in the top-security prison at Belmarsh on the other side of the city, have taken their toll.

Of all the outcomes of the latest hearing, the one that is not in prospect, according to lawyers for Assange, is an appeal to the UK Supreme Court, as it does not handle extradition cases. This is unfortunate because, as became clear on the first day of the hearing, the issues at stake touch on a whole slew of utterly fundamental principles of justice.

It will, of course, be up to the two judges how many of these points to consider. But they range far and wide, from claims of mistakes and omissions made by the courts that approved Assange’s extradition, to the finer points of the UK-US extradition treaty (which UK lawyers have complained is unfairly weighted in favour of the US).

But a few points can be singled out as perhaps decisive in the case presented by his defence. One is how watertight the US government’s assurances are about Assange’s treatment in custody. Might the US authorities feel free, once they have their man, not only to go back on those undertakings, but to add charges under the catch-all Espionage Act?

Extradition agreements, including the UK-US one, tend to exclude what can be judged to be political offences. Stella Assange argues forcefully that he is a political prisoner, as do his supporters – and it is hard to disagree.

What constitutes espionage? One of Assange’s central arguments, and the one most often cited by the media, is that he is a journalist and publisher – the purveyor and editor of information – not the person who found and took classified information. That was the army intelligence analyst Bradley, now Chelsea, Manning, who was released after serving seven years of a 35-year sentence. The US claims that Assange colluded with Manning, but this is a point of contention, as is the extent to which Assange did or did not redact names and other sensitive information that could have cost lives.

Then there are issues of extra-territoriality – what justifies the US seeking the extradition of a non-US citizens for supposed crimes committed outside the US? And the eternal issue for the media, at least in English law – the matter of public interest. Does the value of the information Assange made public via Wikileaks, in particular what could be seen as evidence of war crimes, and his cooperation with mainstream media outlets outweigh other damage that might have been caused?

These are all issues that remain in contention in many jurisdictions and are likely to remain in dispute even after the fate of Julian Assange is decided. And whether or not Assange’s alleged misdeeds are ruled political, his case will have political fall-out. Primarily, of course, this will be for UK-US relations, but potentially also for relations between the UK and the ECHR.

Might this be the time that the UK finally dares to defy the court in Strasbourg, in the interests of the ‘special relationship’ with Washington? And could this then embolden London to defy Strasbourg again over plans to send asylum-seekers to Rwanda? The reverberations of Assange v Government of the United States of America could go very far indeed.