The midfielder signed a six-year deal at the Bernabeu on Friday, after Madrid met the €38million release clause in his Real Sociedad contract. 

And the 23-year-old insisted that he would do everything he could to live up to that lofty price-tag.

"Today is a very special day for me," he said. "Getting the chance to play here is a very unique opportunity.

"I will give everything for this crest.

"I would like to show my appreciation to Real Sociedad and their fans for everything they've done for me."

Madrid president Florentino Perez also credited Sociedad, and said Illarramendi would be well supported by the Madrid faithful.

"We are happy to welcome Asier Illarramendi to Real Madrid," Perez said. "I would like to show my appreciation to Real Sociedad and their president for making this possible.

"The fans will support you in the good and bad times."