His departure comes as the bank prepares for the major task of integrating TSB, which it acquired for £2.65 billion in July.

Mr Regnier, who joined Santander in March 2022, explained that the TSB integration would extend beyond his intended tenure. He stated: “It had been my intention to move on after four to five years… I have suggested to the board that now would be a good time to find a successor who can see this critical project through to its completion and beyond.”

The bank has now begun the recruitment process for his replacement.

The decision to buy TSB, where Santander outbid Barclays, marked a significant strategic shift. It signalled a renewed commitment to the UK market following a period of uncertainty that saw the bank entertain takeover bids, cut thousands of jobs, and lose its UK chair over disagreements with group leadership. The Spanish parent company had also reportedly grown frustrated with the UK unit’s weaker returns and high costs compared to its other markets.

Santander’s executive chair, Ana Botín, praised Mr Regnier for doing an “excellent job” and reaffirmed the bank’s strategy. She described the TSB acquisition as “a clear statement of intent in our ambition for Santander in the UK”.