The bank has its origins in three constituent companies—Abbey National, Alliance & Leicester and Bradford & Bingley—all former mutual building societies.

Santander purchased Alliance & Leicester in the middle of September 2008,[7] followed by the branches and savings business of Bradford & Bingley, which had been nationalised by HM Government during the 2007–2008 financial crisis.

Formula One driver Lewis Hamilton unveiled the first rebranded Santander branch that day in central London.

[11] The bank retained the London headquarters of Abbey National and renamed other regional buildings under its own name.

[13] The charitable divisions of Abbey, Bradford & Bingley and Alliance & Leicester were brought together to form the Santander Foundation.

In Northumberland Street, Newcastle upon Tyne, for example, there were three branches, which were formerly Abbey, Alliance & Leicester and Bradford & Bingley respectively.

[17] On 9 March 2010, Santander sold the investment and asset management business James Hay to IFG Group for £35 million.

[24] During 2011, the bank put aside £538m to cover claims from customers for the misselling of payment protection insurance (PPI).

[25] The sale was completed on 13 May 2013, though Santander continued to service accounts on behalf of SAV Credit until 1 April 2014.

Recent reports had suggested that the Spanish financial institution was contemplating withdrawing from the UK market, a move that would have significant repercussions for its 14 million customers.

[31] The speculation had been driven by reports suggesting that Santander was considering various strategic options, including a possible withdrawal, amid concerns over high operating costs and regulatory challenges in the UK.

[42] Golfer Rory McIlroy signed a sponsorship agreement with the bank in September 2011,[43] and in February 2013, it was announced that British heptathlete Jessica Ennis-Hill would become a brand ambassador.

In June 2019, TV presenters Ant & Dec were announced as new brand ambassadors, appearing frequently in their television advertising campaigns.