Cryptoqueen who fled China for London mansion to be sentenced over £5bn Bitcoin stash

Police raided Qian's Hampstead rental property and uncovered hard drives and laptops found to be loaded with tens of thousands of Bitcoin - believed to be the single largest cryptocurrency seizure in UK history.

Qian had set up the company through which money was embezzled just four years earlier, in her native China. Lantian Gerui, or Bluesky Greet in English, claimed to use investors' money to mine - or generate - new Bitcoin, and to invest in a range of pioneering technological devices.

But UK police believe this was an elaborate scam, and that Qian's company was simply using promises of high profits to pull more and more investors into the scheme.

"The more information we got about her involvement… that she was actually the leader of the fraud, not just a lower down member… it became obvious that yes she's very clever, she's very switched on, very manipulative, able to persuade a lot of people," Det Con Joe Ryan from the Met told the BBC.

One of her investors, Mr Yu, says he never suspected anything was wrong because the company drip-fed him a portion of his apparent earnings - just over 100 yuan ($14, £10) - every day.

"That made everyone feel really good, it even gave us the confidence to borrow a little more to invest in the company," he says.

He and his wife had initially invested 60,000 yuan ($8,429, £6,295) each. They were told, he says, they would make a 200% profit over two and a half years. They were soon taking out thousands of pounds' worth of loans at interest rates of up to 8%, in order to invest more.

In addition, Mr Yu reinvested his daily payouts back into the company as soon as he received them.

"There was no rule that you had to reinvest your earnings, but I suppose we were just too weak to resist. They just pumped up our dreams… until we lost all self-control, all critical judgment."