British Prime Minister Boris Johnson landed in New York this week on a speedy Royal Air Force jet, bringing his vision of a post-Brexit "Global Britain" to the United Nations.

Then he sat on the tarmac for more than an hour. The captain informed passengers that another VIP's plane was occupying the stand. It was the first hint that Johnson's trip to the U.N.'s General Assembly might not run entirely smoothly.

The annual gathering — a diplomatic-media bear pit where scores of world leaders compete for attention in the middle of a teeming, gridlocked Manhattan — can be a daunting experience for new leaders. But for Johnson it could have been something of a respite: a chance to leave the melodrama of Britain's stalled departure from the European Union behind for 72 hours, show a Brexit-befuddled world that Britain is still a serious global player and cement his relationship with U.S. President Donald Trump.

That was never going to be easy, and it got spectacularly harder on Tuesday, when the U.K. Supreme Court ruled that Johnson acted illegally when he suspended Parliament just weeks before Britain is due to leave the EU on Oct. 31. The 11 justices ruled the suspension "unlawful, void and of no effect."

Absorbing the news before dawn at a luxury New York hotel, Johnson's advisers were taken aback. The damning, unanimous ruling was much worse for the government than they had hoped.

With lawmakers set to return to Parliament on Wednesday, Johnson's trip was abruptly cut short. He flew back to London immediately after his speech to the General Assembly on Tuesday evening — one he was still drafting on Tuesday afternoon.

When he did deliver it, it was decidedly unusual — a vivid screed about the dark dangers of, and then about the utopian possibilities of, an increasingly tech-drenched future.

"Can these algorithms be trusted with our lives and hopes?" he asked, before pivoting to positivity: "I am profoundly optimistic about the ability of new technology to serve as a liberator and remake the world wondrously and benignly."

In the speech, Johnson mentioned Brexit only once — as a pointed aside while recalling the myth of Prometheus, who was chained to a rock by Zeus and sentenced to have his liver eaten out by an eagle for eternity.

"And this went on forever," he quipped, "a bit like the experience of Brexit in the U.K, if some of our parliamentarians had their way."

Earlier, Johnson had soldiered on as if it were business as usual, giving a speech to business leaders and holding a series of meetings with other world leaders.

He brushed aside questions about whether he would resign, said he "strongly" disagreed with the court decision and suggested he might try to suspend Parliament for a second time. He also rebuffed calls by the opposition to resign for misleading Queen Elizabeth II when he told her to give her formal assent to Parliament's suspension.

Rapid movement followed by sudden halts and reversals have long marked the roller-coaster political career of Johnson, who ricocheted between high office and political back benches before becoming prime minister two months ago.

His carefully cultivated air of chaos — the shock of blond hair, rumpled shirt and mumbling self-deprecation — led many to write him off as a national leader.

But he got the U.K's top job when Britain's political deadlock over Brexit finally exhausted his predecessor, Theresa May. Johnson promised the governing Conservative Party he would deliver Brexit on the scheduled date of Oct. 31 "do or die."

Since then, Johnson has run straight into the morass that entrapped May: a country split down the middle between supporters and opponents of Brexit, and a Parliament that has rejected the divorce terms on offer but also opposes leaving without a deal.

He is stuck and — alarmingly for a politician who wants to be liked — he's divisive. Outside the Supreme Court in London last week, some Brexit supporters chanted "Boris is our leader." But pro-European Britons spit out his name in conjunction with crude expletives.

Even before the court ruling, Johnson had a rough few weeks. Parliament passed a law to bind his hand, ordering the government to seek a delay to Brexit if it doesn't approve a deal with the EU by late October. Two ministers quit his Cabinet over Brexit — one of them his own younger brother, Jo Johnson.

He was accused in the Sunday Times of giving public funding to a female friend (he denies wrongdoing) and was berated by the father of a sick child on a visit to a hospital.

But speaking to reporters on the plane to New York, Johnson seemed relaxed and more self-aware than he often appears in public. He shrugged off the hospital confrontation, saying there was nothing wrong with "a spot of lively interchange with members of the public."

Johnson's successful stint as mayor of London between 2008 and 2016 shows that he can be an effective ambassador for the U.K. But his message in New York — that post-Brexit Britain will be "more global, more outgoing and more open to the rest of the world than ever before" — was drowned out by the crisis engulfing him in London.

Still, Downing Street officials insisted the trip had been a success, pointing to a joint U.K.-France-Germany statement blaming Iran for the attack on Saudi oil facilities and urging Tehran to comply with its nuclear responsibilities.

Johnson's friends say it would be unwise to write him off just yet. His most prominent friend at the U.N. was Trump, who may see in Johnson a leader with a divisive style — and woes — to match his own.

The two men have significant differences, especially on tackling climate change, a priority for Johnson. But the president was effusive when they met on Tuesday.

"I know him well. He's not going anywhere," Trump told reporters. "Don't worry about him."