The fines break down to £29.75m from the FCA and £18.90m from the PRA after the bank qualified for a 30% discount for agreeing to resolve the fine.

TSB’s charge sheet includes failures in its technical implementation of its new IT systems, which occurred in April 2018.

“While the data itself migrated successfully, the platform immediately experienced technical failures. This resulted in significant disruption to the continuity of TSB’s banking services, including branch, telephone, online and mobile banking,” says the Bank of England.

It adds that a “significant proportion” of TSB’s 5.2m customers were affected by these issues, and that it took until December 2018 for things to get back to normal.

FCA executive director of enforcement and market oversight Mark Steward says: “The failings in this case were widespread and serious which had a real impact on the day-to-day lives of a significant proportion of TSB’s customers, including those who were vulnerable.

“The firm failed to plan for the IT migration properly, the governance of the project was insufficiently robust and the firm failed to take reasonable care to organise and control its affairs responsibly and effectively, with adequate risk management systems.

And PRA chief executive and deputy governor for prudential regulation Sam Woods comments: “The PRA expects firms to manage their operational resilience as well as their financial resilience.

“The disruption to continuity of service experienced by TSB during its IT migration fell below the standard we expect banks to meet.”