Tesco Bank has refunded £2.5 million to 9000 customers who fell victim to a fraud that siphoned money from their current accounts over the weekend.
The number of victims of the attack are less than half the 20,000 initially thought to have been hit.
The bank's move to refund accounts and resume full services following an earlier suspension of all transactions comes just 12 hours after FCA chief Andrew Bailey told MPs that the breach of the bank was "unprecedented in the UK".
Precise details of the assault, billed by Tesco Bank CEO Benny Higgins as "a systematic, sophisticated attack", have yet to be revealed, although the bank has pinpointed the security hole.
In a statement, Higgins says that no personal data was compromised and that the bank is working with the National Crime Agency and regulators to track down the fraudsters.