As he tucked into a New York strip steak and Thumbelina carrots in an ornate private dining room at Mar-a-Lago, Donald Trump knew the bombs would be in the air by the time he finished his chocolate sorbet.

Before sitting sown to eat the president had given the order to launch 59 Tomahawk cruise missiles into Syrian airspace, but the show had to go on.

Mr Trump took his place next to his guest, Chinese leader Xi Jinping, at a long table festooned with flowers and elaborate candelabras. He chatted amiably with Mr Xi and his wife Peng Liyuan, and gave nothing away while the Chinese delegation sipped a 2014 Girard Cabernet Sauvignon from the Napa Valley.

At this pivotal moment for Mr Trump's young presidency the aides he chose to be at the table with him included his daughter Ivanka, chief of staff Reince Priebus, and Wilbur Ross, his commerce secretary. Jared Kushner, his son-in law, was given pride of place at the other side of the Chinese couple. Steve Bannon his chief strategist was toward the end of the table.

At around 8.40pm, when the Tomahawks were launched from the USS Ross and USS Porter in the eastern Mediterranean, Mr Trump was finally able to tell Mr Xi what was on his mind. The Chinese motorcade left Mar-a-Lago 11 minutes later, speeding past palm trees to a nearby hotel.

The march toward bombing Syria had begun on Wednesday afternoon with a meeting of the National Security Council in the Oval Office in the White House.

Mr Trump's reaction to Bashar al-Assad's sarin attack in Idlib the previous day had been visceral.

He chaired the meeting and James Mattis, his defence secretary, laid out a spectrum of options for military retaliation. They ranged from using cruise missiles to target the Shayrat airfield where the sarin attack was launched from, to an assault on numerous airfields, completely grounding Assad's air force, taking out Syrian air defences, or a wider blitz on Assad's entire military and chemical capabilities.

According to officials Mr Trump woke up on Thursday morning having decided he would launch missiles. Among the first to know there would be a strike that night were Mr Mattis, national security adviser HR McMsster, and Secretary of State Rex Tillerson.

Those three men joined Mr Trump on Air Force one as he headed for Mar-a-Lago on Thursday afternoon and were among the advisers huddling with the president in his cabin.

At one point on the flight Mr Trump emerged to speak to journalists on the plane, and denied a decision had been made. But he stood next to a TV screen showing Darth Vader in a Star wars film, which some took it to be an omen. Later, the turbulence on the flight became so bad press secretary Sean Spicer was knocked off his feet.

Arriving at Mar-a-Lago shortly before 3pm Mr Trump and his team engaged in frenetic last minute preparations, some of it in a tent containing secure equipment for communicating with Washington. Aides worked feverishly on Mr Trump's after-dinner speech in which he was to announce the strike. He had decided to launch missiles against Shayrat, which was at the conservative end of the options offered by Mr Mattis. Mr Trump was believed to have made his final decision around 4pm.

There had been numerous phone calls to the UK Foreign Office and Ministry of Defence during the day, and Theresa May had been briefed that the prospect of US military action was becoming more probable.

At midnight UK time, about 10 minutes before Mr Trump and Mr Xi sat down to dinner at Mar-a-Lago, Mr Mattis called Michael Fallon, the British defence secretary, to give him advance notice that the president had given the order. Mr Fallon had stayed in his office to monitor the air strikes.

He said there had been no request from Washington to join the strike, adding: "The United States made it clear that this was to be a United States operation."

Mrs May was informed at the same time by the White House, while Boris Johnson was told by Mr Tillerson.

About half an hour after the British were told, while Mr Trump was in the middle of dinner, the Russian military was informed of the impending US action through a "deconfliction" channel designed to avoid the two major powers taking out each other's forces. It was a warning for Russia to remove any of its planes from the area.

After finishing dinner, and saying farewell to Mr Xi, Mr Trump moved to an improvised situation room within the Spanish-style walls of Mar-a-Lago for an update on the strike.

He was photographed watching a screen with a dozen of his closest advisers at 9.15pm. Moments later he emerged and delivered his public statement on the strike, saying: "God Bless America and the entire world."