Dark Web hacker Grant West was the first cyber crook arrested in Britain with his fingers on a keyboard.
Undercover police snatched his encrypted laptop before he could log out while he was travelling on a train between Wales and London.
A detective sitting next to West waited until he logged on to his computer and then signalled colleagues to move in.
The information on the laptop enabled detectives to unravel his online crimes as part of a two-year investigation.
West, 25, of Minster-on-Sea, Kent, UK, admitted two counts of conspiracy to defraud, unauthorised modification of a computer, separate offences of offering, attempting and possession with intent to supply cannabis, criminal property and money laundering.
He will be sentenced at Southwark Crown Court later this month.
Police also seized £500,000 in Bitcoin West had hidden in several accounts around the world.
The authorities were alerted to West’s criminal activity when several customers of takeaway food app Just eat reported a phishing email seeking their bank details to police.
Detectives discovered West had hacked into the accounts of 200 major online retailers and stolen the details of 78 million customers.
Using the tag ‘Courvoisier’, West sold the financial details of his victims to criminals on the Dark Web for thousands of pounds.
His ‘customers’ paid him in Bitcoin which he spent on a lavish luxury lifestyle, including a £40,000 Audi car and regular trips to Las Vegas, where he gambled and spent money on prostitutes.
Cash in a caravan
West was aided by his girlfriend Rachel Brookes, who lent him her laptop to carry out his crimes.
She admitted conspiracy to defraud but escaped jail with a two-year community service order.
This led to his undoing, as police traced an electronic trail back to her computer and IP address of her router at home.
West also bought and sold cannabis online.
Despite loving the high life, West lived in a caravan, where police found £25,000 in cash. In nearby storage units he rented, they also found half a kilo of cannabis.
Detective Chief Superintendent Mick Gallagher, head of the Metropolitan Police’s Organised Crime Command, said West’s arrest followed “old-style detective work, covert methods and high-end cyber work.”