IT was supposed to last 60 minutes but went on for nearly two and a half hours.

At one point, an exasperated Melania Trump entered the heavily-guarded room and suggested to her husband that he get a move on as there was a G20 concert to go to. But Donald is not known for taking orders and his first sit-down meeting with Vladimir Putin rambled on for another hour.

"There was just such a level of engagement and exchange, neither one of them wanted to stop," revealed Rex Tillerson, the US secretary of state.

The talks covered a lot of ground and had a tangible outcome: a proposed ceasefire in southwest Syria.

The two leaders had spoken before but this was different; it was their first “eyeball-to-eyeball” encounter.

“Phone conversations are obviously not enough," declared Mr Putin. To address important international issues, "that will really need personal meetings," he insisted, adding: “I'm delighted to meet him personally."

As the world’s two most powerful men met, the world was watching for signs of weakness, strength, hostility, friendship. How would they get on after so much media hype?

In the summit conference room were just the presidents, their foreign secretaries, Mr Tillerson and Sergei Lavrov, and the interpreters.

The two leaders appeared formal but relaxed, sitting forward in low-backed armchairs. At one moment, they leaned in closer to have a private word but then quickly moved farther apart to size each other up.

The American President said it was "an honour" to be with Mr Putin.

“We’ve had some very, very good talks. We’re going to have a talk now and obviously that will continue. We look forward to a lot of very positive things happening for Russia and for the United States and for everyone concerned,” he declared.

His hands clasped, Mr Trump volunteered no details about what issues he and the Russian leader had discussed, describing them only as "various things".

Mr Putin slightly hunched in his chair, rubbed his fingers together as he listened to his American colleague address the reporters.

The Russian premier was similarly vague about the extended meeting, telling reporters through a translator that they were discussing international problems and bilateral issues. But he described the fact they were meeting as a positive sign in itself.

However afterwards, word began to seep out about what the two presidents had discussed.

Mr Tillerson said the US President had “pressed Putin more than once” about the claims of Moscow hacking the American presidential election. It had, he stressed, been a “very robust and lengthy exchange”. The two leaders tentatively agreed not to meddle in each other's elections in the future.

The US secretary of state said the cyber-hacking issue had been a “substantial hindrance in the ability to move the US-Russian relationship forward". He revealed how the two countries had agreed to establish lower-level talks to work out details of an agreement and how to monitor compliance. "How do we create a framework in which we have some ability to judge what is happening in the cyber-world and who we can hold accountable," Mr Tillerson explained.

Mr Lavrov later suggested that Mr Trump had accepted Mr Putin’s assurances that Moscow had “not meddled in the US election”.

It also emerged that Washington and Moscow had reached an agreement for a ceasefire in southwest Syria to take effect on Sunday at noon Damascus time.

The deal marks a new level of US involvement in trying to resolve Syria’s civil war, particularly as the two countries have backed opposing sides in the conflict.

Earlier, the summit had been dominated by the issue of trade and Mr Trump’s “America First” policy.

Angela Merkel, the German Chancellor, admitted the discussions had been “very difficult; I don’t want to beat about the bush with that”.

She explained that negotiators “still have a great deal of work ahead of them” to reach an agreed passage on trade in the summit’s closing communique, adding that most participants called for “free but also fair trade” and underlined the significance of the World Trade Organisation.

Xi Jinping, the Chinese President, called on G20 members to support an open world economy and a “multilateral trade regime” amid fears over mounting protectionist pressures, particularly from America.

He said: “We must remain committed to openness and mutual benefit for all so as to increase the size of the global economic pie.”

Another fraught subject was the US Government’s decision to withdraw from the Paris climate change accord. Mrs Merkel noted simply how “most” of the G20 participants had supported it.