In an impressive security move, London bank staff left the keys to their branch on top of a cash machine outside.
Honest passer-by Paul Andrews spotted the keys, realised they unlocked the front door of NatWest, and rang police to tell them of his potentially valuable find.
'I'm still trying to open an account with the bank and I certainly wouldn't hold this against it,' he added. 'Everyone makes mistakes.'
NatWest insisted customers' money was not at risk as the branch in Pinner, North-West London, 'remained fully alarmed throughout'.