LONDON (AP) — British bank NatWest was fined 264.8 million pounds ($354.30 million) on Monday for failing to comply with money laundering rules in a case that marked the first time U.K. financial regulators pursued criminal charges for such violations.

The fine was handed down at Southwark Crown Court in London. NatWest, the partially state-owned bank formerly known as Royal Bank of Scotland, had pleaded guilty on Oct. 7 to charges related to deposits made by a jewelry business between 2012 and 2016.

Over the course of the relationship, the customer deposited 365 million pounds with the bank, about 264 million pounds of it in cash, the U.K.'s Financial Conduct Authority said in a statement. Although some NatWest workers reported suspicions about the transactions, the bank failed to take appropriate action, the regulatory agency said.

"NatWest is responsible for a catalogue of failures in the way it monitored and scrutinized transactions that were self-evidently suspicious," Mark Steward, the FCA's executive director of enforcement, said in a statement. "Combined with serious systems failures, like the treatment of cash deposits as checks, these failures created an open door for money laundering."

The offenses related to operational weaknesses between 2012 and 2016, and involved Fowler Oldfield, a jeweler in Bradford, England.

The case represented the first time the Financial Conduct Authority pushed through a criminal prosecution under money-laundering regulations introduced in 2007. No individuals were charged as part of the proceedings.

"We deeply regret that we failed to adequately monitor one of our customers between 2012 and 2016 for the purpose of preventing money laundering,'' NatWest CEO Alison Rose said. "While today's hearing brings an end to this case, we will continue to invest significant resources in the ongoing fight against financial crime."