Shares in retail bank TSB jumped more than 11% in value after public trading in the Government-back lender started.
The list price of 260p was quickly up to more than 290p, 11.5%, within minutes of trades commencing at 8am.
In early afternoon trades on Friday the price had climbed further, to 294p, before easing back to 290p at the close.
The initial pricing of 260p, slightly above the mid-range estimate, valued the new retail bank at £1.3bn.
Lloyds Banking Group originally planned to offer 25% of TSB shares but upped the figure to 35% after keen interest was shown by investors.
A total of 175 million shares have now been offered to the public.
Lloyds is still 25%-owned by the British taxpayer after a multi-billion bailout in the financial crisis.
Lloyds chief executive Antonio Horta-Osorio said: "The successful initial public offering of TSB is an important further step for Lloyds Banking Group as we act to meet our commitments to the European Commission.
"The significant investor demand for shares in TSB, which reflects investors' confidence in the prospects for the business, has meant that we have been able to set the offer size at 35%.
"TSB has a national network of branches, a strong capital base, robust liquidity and significant economic protection against legacy issues."
EU regulators ordered to Lloyds to sell 631 branches in 2009 over competition concerns, and must now sell the remaining holding by the end of 2015.
The original buyer of the branches was to be the Co-op Bank, until a £1.5bn capital black hole was discovered in the mutual's books.
The share price range was initially set at between 220p and 290p, on June 9.
At the time, Lloyds said in a statement that the float would commence around June 24.