TSB suffered an embarrassing IT failure that left some of its millions of customers unable to access accounts online - just as the bank was being re-launched on the high street for the first-time in 18 years.
Plans for a "seamless" transition were scuppered and a major publicity blitz overshadowed after a glitch meant customers were unable to log on to internet banking at both TSB and parent bank Lloyds.
The problems eclipsed a launch event at one of the 631 branches of the new bank in central London hosted by chief executive Paul Pester.
Mr Pester set out to explain how the TSB would be "fundamentally different" from its competitors and a return to "local banking" as he signalled that he was preparing to ditch the culture of sky-high banker bonuses.
He said the new business would steer clear of investment banking, derivatives trading and overseas speculation while seeking a "new approach" to paying executives - though he declined to disclose his own salary.
Meanwhile, current account customers looked set for disappointment as Mr Pester played down the likelihood that TSB would offer an improved rate when it sets out new products next year.
TSB is now Britain's eighth largest high street bank as it begins reappearing across Britain as a standalone brand for the first time since 1995, when it merged with Lloyds.
Lloyds, rescued by the Government in the financial crisis, has revived the name after being forced to ditch 631 branches under European rules on state aid. The branches are all expected to re-open under the TSB brand over the first three days of this week.
However, a pledge by Lloyds chief executive Antonio Horta-Osorio that there would be a "seamless transition" for customers was undermined on day one of the transfer by the IT glitches.
They followed earlier teething troubles when customers tried to log on over the weekend, and which the bank said has been ironed out.
A spokeswoman said: "We are experiencing an issue with our internet banking service this morning, which has affected the ability of some customers to log on successfully.
"We are working to resolve this as quickly as we can and we apologise to customers for the inconvenience this will have caused. Our branches, telephone banking and cashpoint facilities have not been affected in any way."
The websites were later back up and running, the spokeswoman said.
It is a far cry from the foundation of the Trustee Savings Bank movement by the Reverend Henry Duncan in Scotland more than 200 years ago.
Mr Pester claims to have been inspired by the example of the bank which was founded to serve the community in Ruthwell, Dumfriesshire.
He said customers would appreciate the transparency of knowing where their deposits were being spent as he set out to establish the TSB as a reliable high street business distanced from the reckless investment banking blamed for the financial crisis.
"Their money's not being used in investment banking, derivatives trading or overseas speculation," he said. "They want to know that every penny that's put into the bank will be used to fuel the local economy."
He said a review had found sky-high bankers' pay was a key concern of customers and that he would be asking the board to make changes based on this.
"I will be recommending a new approach to paying me and to paying our senior execs," Mr Pester said.
TSB, which now has 4.6 million customers, said deposits would be used only to fund "mortgages and loans in local communities" or to help small businesses grow.
Mr Pester said: "TSB is fundamentally different from every other bank in the UK."
He attempted to paint the relaunch as a new era in the industry after "banks became slightly disconnected from the communities they were meant to be serving".
By the end of the year, TSB will start publishing data about how it is helping local economies. he added, but he said the bank was not committing to reinvest money saved in one area in that same area.
Mr Pester also said that while TSB did not deal with "large corporates", there was no upper limit on the size of firms who could be customers.
TSB will for the time being offer the same deals as its parent company - which offer no interest on current accounts unless customers meet the conditions of an Enhance account.
Asked whether this would improve, Mr Pester set out the costs faced by banks for running current accounts such as charges for using rivals' cash machines
It emerged earlier this year that 4,000 customers opted to stay with Lloyds.
Updated figures were not available but executives said it was still in the low thousands. Those who remain will have to change account number and sort code, unlike those being automatically switched.
TSB customers will be able to access accounts at 10,000 post offices as well as the bank's own branch network, Mr Pester said.
The new bank, which will have 8,500 members of staff, also means an end to the Cheltenham and Gloucester brand which was owned by Lloyds Banking Group and whose branches will be swallowed up by the TSB.
TSB is expected to float on the stock market next year.
Martin Lewis of Moneysavingexpert.com expressed scepticism about what the new bank could offer.
"TSB may be a new bank today, but it doesn't have any new products," he said. "This means its customers are mostly sitting on the same old Lloyds bank accounts, savings and credit cards, with rates so low the best buy tables giggle with mirth."