NATHAN HUNT: There is no Greensill Capital without Lex Greensill. So who is this guy? Where did he come from? And what motivated him to get as far as he did? And in that case, there's a few million dollars of maybe somebody who has got a little bit more than that has been poured into these funds, which have been sold as ultrasafe, but in fact, they aren't really. They're full of risky loans. And so Credit Suisse played a really important role in fueling Greensill Capital growth, but also spreading the risk to people who didn't understand what they were getting into. In the centuries since, factoring became part of the supply chains that grew around the world, oiled by liquidity. As these operations became faster and more complex they needed not just factoring but reverse factoring, in which people sell their debt, rather than their credit, and each agent in the chain is paid straight away. The process became computerised, and modern global trade now runs on a silent river of digitised debt. NATHAN HUNT: Duncan, you've been following the Greensill story for years. I'm wondering how early did you know that this story wasn't going to end well? And for a form of Prime Minister who really only has his reputation to sell his credibility and his reputation to have put it all on this company, which was already showing some serious red flags, that was a really strange move.

As the Conservative Party self-immolates in the wake of the public’s final loss of patience with the Prime Minister, Duncan Mavin’s new book, The Pyramid of Lies: Lex Greensill and the Billion-Dollar Scandal, is a useful reminder that the creeping (now overwhelming) impression of tawdriness in public life did not begin with Boris. The opportunity to indulge such fantasies seems a long way from the likely day-to-day tasks and responsibilities of a prime minister – and some former associates wonder whether he is cut out for the job.

Pyramid of Lies: The Prime Minister, the Banker and the Billion Pound Scandal

Mr Johnson last week issued a “humble and sincere” apology to Lord Geidt, his ethics adviser, for withholding the messages from an inquiry. Tory sleaze The past few months have proven difficult for the Prime Minister, with Mr Johnson forced to face a series of lobbying scandals within his own party that refreshed accusations of “Tory sleaze”. Mr Guppy ended up being jailed for a separate fraud and Mr Johnson later dismissed the call as a joke. I think things could certainly have been handled better, let me put it that way, by me,” he said in November.

Lex, he had a small bank in Germany, but he wasn't a bank. He needed to find funding from somewhere to pay for these supply chain finance transactions. And so he was looking for investors for that. And Credit Suisse came along and became the biggest investor in those funds. So Lex had sort of latched on to them around 2017, found a couple of portfolio managers, persuaded them that supply chain finance was a great asset class. It paid a little bit more yield than money market funds, but done properly, it could be just as safe or just a little bit riskier. NATHAN HUNT: I have to wonder what on earth was the former Prime Minister of the U.K. David Cameron doing wrapped up in Greensill Capital. Why was he involved in this? A few years ago, I made it into an intimate meeting at the "top table". Just me and the top brass. I had prepared copious notes to discuss the large deal that was imminent. But I hadn't prepared to discuss horse racing, the ownership of horses, or the best dogs to keep at stables. And so they're kind of leaning on each other. And if you take one -- takes the other away, then it all collapses. At Greensill Capital, absolutely Lex and the other executives know that this is a problem. They discuss it all the time in management meetings, how are they going to kind of get out of this problem. Lex being the optimist at all these management meetings will say, leave it to me, I've got it sorted, we'll outgrow this. Of course, they couldn't. Pyramid of Lies charts the meteoric rise and spectacular downfall of Greensill and his company. He had a simple idea - democratising supply chain finance - and disrupted a trillion dollar industry in the process. But a staid business model concealed dubious practices as Greensill made increasingly risky loans to fraudulent companies using other people's money.Cameron was an authentic member of the upper class who might polish him up. After he destroyed his career and the country’s prospects by taking the UK out of the EU by mistake, Cameron yearned for a comfort Lex Greensill could offer him: obscene amounts of money. While still the editor of The Spectator, Mr Johnson won the Conservative seat for Henley in 2001. He enjoyed a rapid ascent through the Commons, becoming shadow arts minister in 2004. He has never issued a public apology to Ms Wyatt. Her mother later claimed Ms Wyatt was forced to have an abortion as a result of her relationship with Mr Johnson. Jennifer Arcuri Boris Johnson has never publicly admitted to his alleged affair with US tech entrepreneur Jennifer Arcuri (Photo: Eugene Metreveli)

And I think they looked at Lex Greensill and said, yes, this guy -- there's some challenges with this guy. Yes, he tends to double down on risky things. He tends to make every loan we can rather than be a bit more discerning. But that's our job, right? Our job is to invest in these people and then shape them the way that we think they should be running their businesses. In this case, they couldn't do that, right? And so that was an error on their part. That's my view anyway.And it's a question I took to Credit Suisse, and I took to SoftBank as a journalist many times. It was so startlingly problematic. In the end, The Bond & Credit Co. was taken over by a company -- Japanese insurer, Tokio Marine. And when Tokio Marine got involved, they looked at The Bond & Credit Co's exposure to Greensill and the Green -- the funds that were investing in Greensill assets. And they said, hey, this is too much. We don't want to do this anymore. And that really spelled the end, right, because without that insurance, the funds that have invested in Greensill's assets, they're no longer able to go out to the same pool of investors. Here are all the excuses Mr Johnson has used to explain away the scandals that have dogged his career: Making up quotes The Pyramid of Lies is not elegantly written. The breathless tone of some descriptions verges on comical: the Savoy, where Greensill holds a breakfast meeting, is “a 130-year-old art deco masterpiece, dubbed London’s 'most famous hotel’ and renowned as a favoured haunt of kings and presidents, Hollywood stars and fashionistas”. It is nonetheless worth reading as a meticulously researched and enjoyably lively account of this major financial scandal. So he grew up in a fairly remote part of Australia, a place called Bundaberg, which is a farming community. His grandfather had started a farm there in the 1940s. And Lex was kind of second, third generation, who was running this farm, mostly farming, sweet potatoes and water melons and things like that. He was clearly kind of a bright guy, a little bit nerdy possibly at school and a sort of fairly rough macho environment that meant he stood out a little bit.

Johnson in Liverpool after being sent to Merseyside to apologise for a leading article in the Spectator. Photograph: Martin Argles/The Guardian DUNCAN MAVIN: Yes, I think that's right. I think this is -- it's tempting sometimes to see these big kind of corporate scandals in terms of big systems and institutions. But at the heart of this one, is the guy Lex Greensill. And he's fascinating, a really divisive character. Some people I talked to said Lex is really charismatic and a genius. And other people I talked to said, stay away from Lex, things are going to go wrong.

Lex Greensill had a simple, billion-dollar idea - democratising supply chain finance. Suppliers want to get their invoices paid as soon as possible. Companies want to hold off as long as they can. Greensill bridged the two, it's mundane, boring even, but he saw an opportunity to profit. However, margins are thin and Lex, ever the risk taker, made lucrative loans with other people's money: to a Russian cargo plane linked to Vladmir Putin, to former Special Forces who ran a private army, and crucially to companies that were fraudulent or had no revenue. To its founder, Greensill Capital is more than a business: his whole new identity depends upon it. As the story unfolds, we see his drive and determination evolve fatally into messianic ambition and a blinkered disregard for differing views.