A NatWest bank manager gave £830,000 to a fraudster posing as a 91-year-old customer 'because he wanted to eat his fish and chips', a court heard.
Umar Mughal, 27, approved the bogus transfer of the funds at the Brentwood branch in Essex where he worked.
He allegedly failed to carry out any checks to confirm the identity of the man who came into the branch on May 9 2012 claiming to be a wealthy client.
Mr Mughal put his error down to the 'negative atmosphere' in the bank, while also claiming that he was trying to have his lunch at the time of the incident.
Financial investigator Julia Payne told the Old Bailey that when the bank's system was examined there was no sign that Mr Mughal had confirmed the customer's signature.
She continued: 'From a banking perspective people working in the branches know we could be targeted by a fraudster and to look at documentation to see if it is genuine.'
Ms Payne added: 'The computer trail tells us what enquiries have been made in the account.
'As soon as Mr Mughal sat down he entered the sort code and account number.
'I would have expected to see a signature enquiry as that's how Mr Mughal told me he identified the customer.
'But the first thing after that is the funds transfer.'
She said: 'There is no looking into the account for signatory or anything of the kind.'
Prosecutor Fer Chinner said: 'The man comes into the branch and the transfers are made by Mr Mughal.
'Mughal logs on to the computer system at 14.07 and logs off at 14.34.'
She said that Mr Mughal accessed five different accounts during the session and transferred the money into one account.
Jurors heard £70,000 was taken from the first account, £10,325 from the second, £73,300 from the third, £23,100 from the forth and £76,600 from the final account.
The suspicious activity was spotted by the customer's private banking manager the following day who raised the alarm, it is said.
Ms Payne said: 'The customer had a private banking manager, customers with large balances as he had would have a banking manager.
'He noticed the large number of transfers the next day.'
She added: 'He first contacted the branch and spoke to Mr Mughal to find out what had happened.
'Mr Mughal explained that the customer had come in.'
Mr Mughal was investigated by the bank and claimed during an interview on May 10 2012 that he had 'made a mistake', the court heard.
He allegedly tried to blame his colleagues for 'moaning all day' and creating a 'negative atmosphere'.
During questioning, he said: 'I've done one stupid little thing which for me was a stupid thing but for the bank was massive.
'I never make the same mistake twice and unfortunately this mistake was big.'
He added: 'When it comes to this transaction do I want to put it on here that I gave £800,000 to someone else because I wanted to eat my fish and chips?'
Ms Payne asked him: 'Is that why?'
Mr Mughal replied that he wanted to take his break and 'ignored' the procedure for customer identification.
He added: 'I just wish I could turn back time and do my job again like I normally do.'
Mr Mughal, of Walthamstow, east London, denies fraud by abuse of position.
The trial continues.