When Donald Trump officially announced that he was running for president of the United States, on June 16 2015, he was 110.00109/1 on the Betfair Exchange to succeed Barack Obama in the White House.
For several months, Trump had been making controversial statements about immigration, Muslims and terrorism. He'd been an outspoken critic of Obama's administration, peddling claims about the president's birth certificate and, following Obama's election victory in 2012, advocating an armed uprising against the US government.
What an earth was the millionaire star of the American Apprentice up to? Surely he was jeopardising his TV career and business interests with these antics. He had no chance of winning the presidency, as the odds showed, and with his self-financed campaign was destined to lose a fortune.
Jeb Bush, Marco Rubio and Chris Christie were among the leading candidates, and they had actual political experience, so one of them was expected to win the Republican nomination. But it didn't really matter who got the nod because everyone knew that the Democratic Party's Hillary Clinton would be America's next president. As a former-first lady, senator and secretary of state, Clinton was the most qualified candidate in history. No wonder she traded at 1.774/5 on the Exchange to win the White House on New Year's Day 2016.
Trump's road to the nomination
By the time the primaries came around in early 2016, Trump looked like a more credible contender - not for the White House (to this day he hasn't mastered that) but for the Republican nomination.
The traction Trump was getting, though, was merely a reflection of the failings of the other candidates who looked like squares, as they struggled to compete with his "Make America Great Again" campaign slogan and unorthodox debating style. Still, it was Ted Cruz, the senator from Texas, who won the opening caucus in Iowa and looked like the candidate with the momentum.
That changed when Trump won the New Hampshire primary and his odds shortened to 6.05/1 for the presidency. They drifted to 11.5, however, a month or so later when he made incendiary comments about abortion. The Republican establishment, which included former-presidents and presidential candidates, were desperate for him not to be the party's pick and united in an "Anyone but Trump" campaign.
But registered Republicans kept voting for Trump in the primaries and he was confirmed as their presidential candidate on 24 May at which point he was 3.02/1 for the White House.
Was Brexit a sign?
A month later, the first of several seismic political shocks took place across the Atlantic when Britain stunned the world by voting to leave the European Union in an in-out referendum - a result that traded at 4.216/5 the day before voting.
Trump, like right-wing populists around the world, hailed the UK referendum result as an example of people rising up against an out of touch political establishment. He would later invite Nigel Farage, dubbed "Mr Brexit" among American libertarians, to campaign for him.
With hindsight, the result of the in-out referendum looks like a sign that the normal rules, by which western democracies had been governed for the past half-a-century, no longer applied. But at the time it still seemed implausible that Trump could win the White House.
The controversies that failed to stop Trump
While Trump was promising to build a wall at America's southern border, and ban immigration from Muslim countries, Clinton was waging a professional, if lacklustre, campaign. Despite the interesting emergence of a left-wing rival in Bernie Sanders, she sealed the Democratic Party nomination in straightforward style and the party looked set to unite behind her.
Clinton also looked to be the beneficiary of Trump's campaign which was lurching between disasters on an almost hourly basis. That changed in August when Trump hired Breitbart chief Steve Bannon to take the reins. Bannon, along with Kellyanne Conway, have largely been credited with turning around Trump's bid for the presidency.
They could do nothing to stop the leak of what came to be known as the Access Hollywood tape. Shot in 2005, it featured a recording of Trump boasting that he had groped women. Most political commentators thought it was the end of Trump's candidacy and his exchange odds duly drifted to 7.26/1. He performed poorly in his three televised debate with Clinton and she shortened to 1.211/5.
Clinton odds-on on election day before dramatic defeat
Trump was thrown a lifeline on 31 October when the FBI reopened its investigation into allegations that Clinton used a private email server for official public communications during her time at the State Department.
It was strange timing and it added to Trump's accusations of "crooked Hillary". Still, her odds only drifted to 1.364/11 and she went into election day on 8 November odds-on to become America's first woman president. Indeed, she traded at 1.081/12 once voting was closed and, when the first results trickled in, Trump traded at 13.012/1.
Pollsters and pundits explained that, for Trump to win he would have to first win Florida, which he was predicted to lose, and then break the Democrats' "blue firewall" of Pennsylvania, Wisconsin and Michigan, which a Republican had not won in a generation. But Trump won Florida, smashed the "blue firewall" by winning all three states and changed his Twitter bio to "President-elect of the United States" shortly after Clinton called him to concede.
There are those, like the Fire and Fury author Michael Wolff, who say Trump neither expected nor wanted to win, that his campaign was designed to give him the platform to launch a TV series on a conservative network. Soon after his election victory, betting opened on when he'd leave office, as plenty of people predicted he wouldn't survive his first year because he was so unsuited to the job and vulnerable to impeachment.
In his victory speech on election night, Trump said: "Now it is time for America to heal the wounds of division."
That healing failed to materialise and this year's election, in which Trump is likely to face the Democrats' Joe Biden, looks set to be one of the bitterest in history.
In the first of our Classic Exchange Stories series, Dave Tindall looks back at Liverpool's incredible comeback against Barcelona in the 2019/20 Champions League semi-final...