Santander has apologised to customers after a widespread outage over the weekend locked UK customers out of their accounts.
The problems, which began on Saturday morning and lasted much of the day until about 21:15, ran across the full gamut of services, from telephone, online and mobile banking, to branches, cards, and cash machines.
In a statement on its home page, the bank says: "We are very sorry for the inconvenience we know this caused.
"Our banking services continue to run as normal, with our branches, call centres and chat service available as usual, however it may take longer to get through on the phone. We appreciate your patience."
Gareth Shaw, head of money at Which?, spoke for many inconvenienced customers: “These technical issues will be causing stress for many Santander customers - with people reporting that they have been unable to make online payments or in some cases purchase food in their local supermarket.
“Customers can incur fines, penalties and fees when they’re not able to access their finances, so the bank must offer compensation to all those who have been impacted in this way.
The bank says it will publish details on social media and its website for customers to claim reimbursement if they were left out of pocket by the down time.
The bank has yet to explain the cause of the outage, although its mobile banking app was due for scheduled maintenance on Friday evening.