The case, the first brought against a UK bank under money laundering regulations overseen by the FCA, focused on NatWest’s failure to “adequately monitor” deposits into its customers accounts, after one person suspiciously received £365 million ($496.54 million), including £264 million ($359.14 million) in cash, over five years.

The bank admitted “relevant operational failures” between 2012 and 2016, accepting it had failed to properly follow anti-money laundering legislation related to Fowler Oldfield, a jeweller that was shut down after a 2016 police raid.

The FCA told a Westminster court that, despite Fowler Oldfield telling NatWest it had a predicted annual turnover of £15 million ($20.41 million) when it became a client, it was, at its busiest, depositing £1.8 million ($2.45 million) a day.

Having pleaded guilty, the FCA warned that NatWest’s “likely sentence is a very large fine,” although it didn’t immediately state how much the bank will be expected to pay for the offence.

NatWest’s chief executive, Alison Rose, said “we deeply regret” that the bank failed to “prevent money laundering by one of our customers.” Pledging to prevent similar issues in the future, Rose accepted “NatWest has a vital part to play in detecting” financial crimes and cited how the bank has “invested significant resources” to combat illegal activity going forward.

NatWest is a state-backed bank that is currently 55% taxpayer-owned, having been given a bailout of over £45 billion ($61.22 billion) during the 2008 global financial crisis to prevent it from collapsing.