High street bookmaker William Hill has been fined £6.2m for failing to make adequate checks of money laundering and problem gambling.
A probe into the turf accountant found that between November 2014 and August 2016 William Hill Group had broken social responsibility and anti-money laundering regulations.
Ten customers were allowed to deposit large sums of money linked to illegal activities because the company had failed to carry out adequate checks, the Gambling Commission has said. The transactions, however, made £1.2m profit for William Hill.
The bookies also failed to carry out adequate checks to stop customers gambling well beyond their means.
One customer who deposited £654,000 in nine months turned out to be living in a rented property and earning £30,000 a year.
Another gambler, who spent £514,000 in 14 months at the bookies, was earning £30,000 a year and stealing from his employer to fund his gambling addiction.
Executive director of the Gambling Commission Neil McArthur said: "This was a systemic failing at William Hill which went on for nearly two years and today's penalty package - which could exceed £6.2 million - reflects the seriousness of the breaches.
"Gambling businesses have a responsibility to ensure that they keep crime out of gambling and tackle problem gambling - and as part of that they must be constantly curious about where the money they are taking is coming from."
William Hill confirmed in a statement on its website that its online business has "entered into a regulatory settlement with the Gambling Commission" following the identification of a number of cases where "former policies" were insufficient to ensure full regulatory compliance.
William Hill CEO Philip Bowcock said: "William Hill has fully co-operated with the commission throughout this process, introducing new and improved policies and increased levels of resourcing.
"We have also committed to an independent process review and will work to implement any recommendations that emerge from that review.
"We are fully committed to operating a sustainable business that properly identifies risk and better protects customers.
"We will continue to assist the commission and work with other operators to improve practices in the areas identified."