In January a court ruled the brothers had won a tender with a cash bid for the complex, net of debt, of 283 million euros (£254 million).

"There's an agreement with the Reuben brothers to buy back the (property)," one of the sources with knowledge of the deal said, adding that it still needed to be signed off.

Santander and the Reuben brothers' office declined to comment.

Neither of the sources disclosed the price of the transaction.

The tender was part of a liquidation settlement of Marme Investments, which bought Santander's headquarters for 1.9 billion euros in a 40-year sale-and-leaseback deal in 2018.

Santander pays millions of euros in monthly rent to the owner of the 250 hectare plot whose nine futuristic buildings include offices, restaurants and a residence for its employees.

(Reporting by Jesus Aguado; Editing by Paul Day and Elaine Hardcastle)