On the day that Royal Bank of Scotland reported its first quarterly profit in 12 years, the sweet taste of success has turned bitter for customers of subsidiary NatWest who have seen transfers from accounts vanish and mobile apps and online banking go dark.
Ongoing since 7.15 am, the calamity couldn't have come at a worse time, hitting on payday for thousands of customers and just as the UK enters a bank holiday weekend.
Customers took to Twitter to vent their frustration, reporting long queues before they could get to speak to someone.
More troubling for other users is the disappearance of transfers from accounts.
And the problem is not just confined to RBS-to-RBS account transfers
NatWest has yet to set a timeline on a fix, stating merely: