Banco Santander SA (SAN) shares surged 5.22% during pre-market trading on Wednesday, following reports about the bank's integration plans for its recently acquired TSB Bank.

The Spanish lender plans to phase out the TSB Bank brand and integrate the business into its UK operations, rebranding it as Santander UK. This follows Santander's completion of a £2.65 billion acquisition of TSB from Banco Sabadell, which adds approximately 5 million customers and over £45 billion in assets to Santander's UK unit.

The acquisition significantly enhances Santander's footprint in Scotland and northern England, marking a strategic expansion of its UK operations that appears to have generated positive investor sentiment.