During a night of heavy drinking at an upscale London bar in May 2016, George Papadopoulos, a young foreign policy adviser to the Trump campaign, made a startling revelation to Australia’s top diplomat in Britain: Russia had political dirt on Hillary Clinton.

About three weeks earlier, Papadopoulos had been told that Moscow had thousands of emails that would embarrass Clinton, apparently stolen in an effort to try to damage her campaign.

Exactly how much Papadopoulos said that night at the Kensington Wine Rooms with the Australian, Alexander Downer, is unclear. But two months later, when leaked Democratic emails began appearing online, Australian officials passed the information about Papadopoulos to their US counterparts, according to four current and former US and foreign officials with direct knowledge of the Australian's role.

The hacking and the revelation that a member of the Trump campaign may have had inside information about it were driving factors that led the FBI to open an investigation in July 2016 into Russia’s attempts to disrupt the election and whether any of President Donald Trump’s associates conspired.

If Papadopoulos, who pleaded guilty to lying to the FBI and is now a cooperating witness, was the improbable match that set off a blaze that has consumed the first year of the Trump administration, his saga is also a tale of the Trump campaign in miniature. He was brash, boastful and under qualified, yet he exceeded expectations. And, like the campaign itself, he proved to be a tantalising target for a Russian influence operation.

While some of Trump’s advisers have derided him as an insignificant campaign volunteer or a “coffee boy,” interviews and new documents show that he stayed influential throughout the campaign. Two months before the election, for instance, he helped arrange a New York meeting between Trump and President Abdel-Fattah el-Sissi of Egypt.

The information that Papadopoulos gave to the Australians answers one of the lingering mysteries of the past year: What so alarmed US officials to provoke the FBI to open a counterintelligence investigation into the Trump campaign months before the presidential election?

It was not, as Trump and other politicians have alleged, a dossier compiled by a former British spy hired by a rival campaign. Instead, it was first-hand information from one of the United States’ closest intelligence allies.

The biggest names involved in the Trump-Russia investigation Show all 17 1 /17 The biggest names involved in the Trump-Russia investigation The biggest names involved in the Trump-Russia investigation Paul Manafort Mr Manafort is a Republican strategist and former Trump campaign manager. He resigned from that post over questions about his extensive lobbying overseas, including in Ukraine where he represented pro-Russian interests. Mr Manafort turned himself in at FBI headquarters to special counsel Robert Mueller’s team on Oct 30, 2017, after he was indicted under seal on charges that include conspiracy against the United States, conspiracy to launder money, unregistered agent of a foreign principal, false and misleading US Foreign Agents Registration Act statements, false statements, and seven counts of failure to file reports of foreign bank and financial accounts. Getty The biggest names involved in the Trump-Russia investigation Rick Gates Mr Gates joined the Trump team in spring 2016, and served as a top aide until he left to work at the Republican National Committee after the departure of former Trump campaign manager Paul Manafort. Mr Gates' had previously worked on several presidential campaigns, on international political campaigns in Europe and Africa, and had 15 years of political or financial experience with multinational firms, according to his bio. Mr Gates was indicted alongside Mr Manafort by special counsel Robert Mueller's team on charges that include conspiracy against the United States, conspiracy to launder money, unregistered agent of a foreign principal, false and misleading US Foreign Agents Registration Act statements, false statements, and seven counts of failure to file reports of foreign bank and financial accounts. AP The biggest names involved in the Trump-Russia investigation George Papadopoulos George Papadopoulos was a former foreign policy adviser for the Trump campaign, having joined around March 2016. Mr Papadopoulos plead guilty to federal charges for lying to the FBI as a part of a cooperation agreement with Special Counsel Robert Mueller's investigation. Mr Papadopoulos claimed in an interview with the FBI that he had made contacts with Russian sources before joining the Trump campaign, but he actually began working with them after joining the team. Mr Papadopoulos allegedly took a meeting with a professor in London who reportedly told him that Russians had "dirt" on Hillary Clinton. The professor also allegedly introduced Mr Papadopoulos to a Russian who was said to have close ties to officials at the Russian Ministry of Foreign Affairs. Mr Papadopoulos also allegedly was in contact with a woman whom he incorrectly described in one email to others in the campaign as the "niece" to Russian President Vladimir Putin. Twitter The biggest names involved in the Trump-Russia investigation Donald Trump Jr The President's eldest son met with a Russian lawyer - Natalia Veselnitskaya - on 9 June 2016 at Trump Tower in New York. He said in an initial statement that the meeting was about Russia halting adoptions of its children by US citizens. Then, he said it was regarding the Magnitsky Act, a US law blacklisting Russian human rights abusers. In a final statement, Mr Trump Jr released a chain of emails that revealed he took the meeting in hopes of getting information Ms Veselnitskaya had about Hillary Clinton's alleged financial ties to Russia. He and the President called it standard "opposition research" in the course of campaigning and that no information came from the meeting. The meeting was set up by an intermediary, Rob Goldstone. Jared Kushner and Paul Manafort were also at the same meeting. Getty Images The biggest names involved in the Trump-Russia investigation Jared Kushner Mr Kushner is President Donald Trump's son-in-law and a key adviser to the White House. He met with a Russian banker appointed by Russian President Vladimir Putin in December. Mr Kushner has said he did so in his role as an adviser to Mr Trump while the bank says he did so as a private developer. Mr Kushner has also volunteered to testify in the Senate about his role helping to arrange meetings between Trump advisers and Russian Ambassador to the US Sergey Kislyak. Getty Images The biggest names involved in the Trump-Russia investigation Rob Goldstone Former tabloid journalist and now music publicist Rob Goldstone is a contact of the Trump family through the previously Trump-owned 2013 Miss Universe pageant, which took place in Moscow. In June 2016, he wrote to Donald Trump Jr offering a meeting with a Russian lawyer, Natalya Veselnitskaya, who had information about Hillary Clinton. Mr Goldstone was the intermediary for Russian pop star Emin Agalaraov and his father, real estate magnate Aras, who played a role in putting on the 2013 pageant. In an email chain released by Mr Trump Jr, Mr Goldstone seemed to indicate Russian government's support of Donald Trump's campaign. AP images The biggest names involved in the Trump-Russia investigation Aras and Emin Agalarov Aras Agalarov (R) is a wealthy Moscow-based real estate magnate and son Emin (L) is a pop star. Both played a role in putting on the previously Trump-owned 2013 Miss Universe pageant in Moscow. They allegedly had information about Hillary Clinton and offered that information to the Trump campaign through a lawyer with whom they had worked with, Natalia Veselnitskaya, and music publicist Rob Goldstone. Getty Images The biggest names involved in the Trump-Russia investigation Natalia Veselnitskaya Natalia Veselnitskaya is a Russian lawyer with ties to the Kremlin. She has worked on real estate issues and reportedly counted the FSB as a client in the past. She has ties to a Trump family connection, real estate magnate Aras Agalarov, who had helped set up the Trump-owned 2013 Miss Universe pageant which took place in Moscow. Ms Veselnitskaya met with Donald Trump Jr, Jared Kushner, and Paul Manafort in Trump Tower on 9 June 2016 but denies the allegation that she went there promising information on Hillary Clinton's alleged financial ties to Russia. She contends that the meeting was about the US adoptions of Russian children being stopped by Moscow as a reaction to the Magnitsky Act, a US law blacklisting Russian human rights abusers. Getty Images The biggest names involved in the Trump-Russia investigation Mike Flynn Mr Flynn was named as Trump's national security adviser but was forced to resign from his post for inappropriate communication with Russian Ambassador to the US Sergey Kislyak. He had misrepresented a conversation he had with Mr Kislyak to Vice President Mike Pence, telling him wrongly that he had not discussed sanctions with the Russian. Getty Images The biggest names involved in the Trump-Russia investigation Sergey Kislyak Mr Kislyak, the former longtime Russian ambassador to the US, is at the centre of the web said to connect President Donald Trump's campaign with Russia. Reuters The biggest names involved in the Trump-Russia investigation Roger Stone Mr Stone is a former Trump adviser who worked on the political campaigns of Richard Nixon, George HW Bush, and Ronald Reagan. Mr Stone claimed repeatedly in the final months of the campaign that he had backchannel communications with WikiLeaks founder Julian Assange and that he knew the group was going to dump damaging documents to the campaign of Democratic candidate Hillary Clinton - which did happen. Mr Stone also had contacts with the hacker Guccier 2.0 on Twitter, who claimed to have hacked the DNC and is linked to Russian intelligence services. Getty Images The biggest names involved in the Trump-Russia investigation Jeff Sessions The US attorney general was forced to recuse himself from the Trump-Russia investigation after it was learned that he had lied about meeting with Russian Ambassador to the US Sergey Kislyak. Getty Images The biggest names involved in the Trump-Russia investigation Carter Page Mr Page is a former advisor to the Trump campaign and has a background working as an investment banker at Merrill Lynch. Mr Page met with Russian Ambassador to the US Sergey Kislyak during the 2016 Republican National Convention in Cleveland. Mr Page had invested in oil companies connected to Russia and had admitted that US Russia sanctions had hurt his bottom line. Reuters The biggest names involved in the Trump-Russia investigation Jeffrey "JD" Gorden Mr Gordon met with Russian Ambassador to the US Sergey Kislyak during the 2016 Republian National Convention to discuss how the US and Russia could work together to combat Islamist extremism should then-Republican presidential candidate Donald Trump win the election. The meeting came days before a massive leak of DNC emails that has been connected to Russia. Creative Commons The biggest names involved in the Trump-Russia investigation James Comey Mr Comey was fired from his post as head of the FBI by President Donald Trump. The timing of Mr Comey's firing raised questions around whether or not the FBI's investigation into the Trump campaign may have played a role in the decision. Getty Images The biggest names involved in the Trump-Russia investigation Preet Bharara Mr Bahara refused, alongside 46 other US district attorney's across the country, to resign once President Donald Trump took office after previous assurances from Mr Trump that he would keep his job. Mr Bahara had been heading up several investigations including one into one of President Donald Trump's favorite cable television channels Fox News. Several investigations would lead back to that district, too, including those into Mr Trump's campaign ties to Russia, and Mr Trump's assertion that Trump Tower was wiretapped on orders from his predecessor. Getty Images The biggest names involved in the Trump-Russia investigation Sally Yates Ms Yates, a former Deputy Attorney General, was running the Justice Department while President Donald Trump's pick for attorney general awaited confirmation. Ms Yates was later fired by Mr Trump from her temporary post over her refusal to implement Mr Trump's first travel ban. She had also warned the White House about potential ties former National Security Adviser Michael Flynn to Russia after discovering those ties during the FBI's investigation into the Trump campaign's connections to Russia. Getty Images

Interviews and previously undisclosed documents show that Papadopoulos played a critical role in this drama and reveal a Russian operation that was more aggressive and widespread than previously known. They add to an emerging portrait, gradually filled in over the past year in revelations by federal investigators, journalists and lawmakers, of Russians with government contacts trying to establish secret channels at various levels of the Trump campaign.

The FBI investigation, which was taken over seven months ago by special counsel Robert Mueller, has cast a shadow over Trump’s first year in office — even as he and his aides repeatedly played down the Russian efforts and falsely denied campaign contacts with Russians.

They have also insisted that Papadopoulos was a low-level figure. But spies frequently target peripheral players as a way to gain insight and leverage.

FBI officials disagreed in 2016 about how aggressively and publicly to pursue the Russia inquiry before the election. But there was little debate about what seemed to be afoot. John O. Brennan, who retired this year after four years as CIA director, told Congress in May that he had been concerned about multiple contacts between Russian officials and Trump advisers.

Russia, he said, had tried to “suborn” members of the Trump campaign.

Papadopoulos, then an ambitious 28-year-old from Chicago, was working as an energy consultant in London when the Trump campaign, desperate to create a foreign policy team, named him as an adviser in early March 2016. His political experience was limited to two months on Ben Carson’s presidential campaign before it collapsed.

Papadopoulos had no experience on Russia issues. But during his job interview with Sam Clovis, a top early campaign aide, he saw an opening. He was told that improving relations with Russia was one of Trump’s top foreign policy goals, according to court papers, an account Clovis has denied.

Travelling in Italy that March, Papadopoulos met Joseph Mifsud, a Maltese professor at a now-defunct London academy who had valuable contacts with the Russian Ministry of Foreign Affairs. Mifsud showed little interest in Papadopoulos at first.

But when he found out he was a Trump campaign adviser, he latched onto him, according to court records and emails obtained by The New York Times. Their joint goal was to arrange a meeting between Trump and President Vladimir Putin of Russia in Moscow, or between their respective aides.

In response to questions, Papadopoulos’ lawyers declined to provide a statement.

Before the end of the month, Mifsud had arranged a meeting at a London cafe between Papadopoulos and Olga Polonskaya, a young woman from St. Petersburg whom he falsely described as Putin’s niece. Although Polonskaya told The Times in a text message that her English skills are poor, her emails to Papadopoulos were largely fluent. “We are all very excited by the possibility of a good relationship with Mr Trump,” Polonskaya wrote in one message.

More important, Mifsud connected Papadopoulos to Ivan Timofeev, a program director for the prestigious Valdai Discussion Club, a gathering of academics that meets annually with Putin. The two men corresponded for months about how to connect the Russian government and the campaign. Records suggest that Timofeev, who has been described by Mueller’s team as an intermediary for the Russian Foreign Ministry, discussed the matter with the ministry’s former leader, Igor Ivanov, who is widely viewed in the United States as one of Russia’s elder statesmen.

When Trump’s foreign policy team gathered for the first time at the end of March in Washington, Papadopoulos said he had the contacts to set up a meeting between Trump and Putin. Trump listened intently but apparently deferred to Jeff Sessions, then a senator from Alabama and head of the campaign’s foreign policy team, according to participants in the meeting.

Sessions, now attorney general, initially did not reveal that discussion to Congress, because, he has said, he did not recall it. More recently, he said he pushed back against Papadopoulos’ proposal, at least partly because he did not want someone so unqualified to represent the campaign on such a sensitive matter.

If the campaign wanted Papadopoulos to stand down, previously undisclosed emails obtained by The Times show that he either did not get the message or failed to heed it. He continued for months to try to arrange some kind of meeting with Russian representatives, keeping senior campaign advisers abreast of his efforts. Clovis ultimately encouraged him and another foreign policy adviser to travel to Moscow, but neither went because the campaign would not cover the cost.

Papadopoulos was trusted enough to edit the outline of Trump’s first major foreign policy speech on April 27, an address in which the candidate said it was possible to improve relations with Russia. Papadopoulos flagged the speech to his newfound Russia contacts, telling Timofeev that it should be taken as “the signal to meet.”

“That is a statesman speech,” Mifsud agreed. Polonskaya wrote that she was pleased that Trump’s “position toward Russia is much softer” than that of other candidates.

Stephen Miller, then a senior policy adviser to the campaign and now a top White House aide, was eager for Papadopoulos to serve as a surrogate, someone who could publicise Trump’s foreign policy views without officially speaking for the campaign. But Papadopoulos’ first public attempt to do so was a disaster.

In a 4 May, 2016, interview with The Times of London, Papadopoulos called on Prime Minister David Cameron to apologise to Trump for criticising his remarks on Muslims as “stupid” and divisive. “Say sorry to Trump or risk special relationship, Cameron told,” the headline read. Clovis, national campaign co-chairman, severely reprimanded Papadopoulos for failing to clear his explosive comments with the campaign in advance.

From then on, Papadopoulos was more careful with the press — though he never regained the full trust of Clovis or several other campaign officials.

Mifsud proposed to Papadopoulos that he, too, serve as a campaign surrogate. He could write op-eds under the guise of a “neutral” observer, he wrote in a previously undisclosed email, and follow Trump to his rallies as an accredited journalist while receiving briefings from the inside the campaign.

In late April, at a London hotel, Mifsud told Papadopoulos that he had just learned from high-level Russian officials in Moscow that the Russians had “dirt” on Clinton in the form of “thousands of emails,” according to court documents. Although Russian hackers had been mining data from the Democratic National Committee’s computers for months, that information was not yet public. Even the committee itself did not know.

Whether Papadopoulos shared that information with anyone else in the campaign is one of many unanswered questions. He was mostly in contact with the campaign over emails. The day after Mifsud’s revelation about the hacked emails, he told Miller in an email only that he had “interesting messages coming in from Moscow” about a possible trip. The emails obtained by The Times show no evidence that Papadopoulos discussed the stolen messages with the campaign.

Not long after, however, he opened up to Downer, the Australian diplomat, about his contacts with the Russians. It is unclear whether Downer was fishing for that information that night in May 2016. The meeting at the bar came about because of a series of connections, beginning with an Israeli Embassy official who introduced Papadopoulos to another Australian diplomat in London.

It is also not clear why, after getting the information in May, the Australian government waited two months to pass it to the FBI. In a statement, the Australian Embassy in Washington declined to provide details about the meeting or confirm that it occurred.

“As a matter of principle and practice, the Australian government does not comment on matters relevant to active investigations,” the statement said. The FBI declined to comment.

Once the information Papadopoulos had disclosed to the Australian diplomat reached the FBI, the bureau opened an investigation that became one of its most closely guarded secrets. Senior agents did not discuss it at the daily morning briefing, a classified setting where officials normally speak freely about highly sensitive operations.

Besides the information from the Australians, the investigation was also propelled by intelligence from other friendly governments, including the British and Dutch. A trip to Moscow by another adviser, Carter Page, also raised concerns at the FBI.

With so many strands coming in — about Papadopoulos, Page, the hackers and more — FBI agents debated how aggressively to investigate the campaign’s Russia ties, according to current and former officials familiar with the debate. Issuing subpoenas or questioning people, for example, could cause the investigation to burst into public view in the final months of a presidential campaign.

It could also tip off the Russian government, which might try to cover its tracks. Some officials argued against taking such disruptive steps, especially since the FBI would not be able to unravel the case before the election.

Others believed that the possibility of a compromised presidential campaign was so serious that it warranted the most thorough, aggressive tactics. Even if the odds against a Trump presidency were long, these agents argued, it was prudent to take every precaution.

That included questioning Christopher Steele, the former British spy who was compiling the dossier alleging a far-ranging Russian conspiracy to elect Trump. A team of FBI agents travelled to Europe to interview Steele in early October 2016. Steele had shown some of his findings to an FBI agent in Rome three months earlier, but that information was not part of the justification to start an counterintelligence inquiry, US officials said.

Ultimately, the FBI and Justice Department decided to keep the investigation quiet, a decision that Democrats in particular have criticised. And agents did not interview Papadopoulos until late January.