Spurs boss Jose Mourinho revealed on Sunday (AEDT) the club was poised to convert the 23-year-old's initial loan move from Real Betis into a full switch, saying the player's form had made it "an easy decision".

The move was completed on Wednesday (AEDT), just as the sale of Christian Eriksen to Inter Milan was officially confirmed.

"We are delighted to announce that we have exercised the option to convert the loan of Giovani Lo Celso from Real Betis to a permanent transfer," Tottenham's statement read.

"Gio has signed a contract with the club until 2025.

"The midfielder has produced impressive performances after establishing himself in the team following a hip injury which restricted his playing time in the early part of his loan."

A superb individual run from Lo Celso helped to set up Spurs' goal as Son Heung-min struck in the 1-1 FA Cup fourth-round draw against Southampton, a game in which he also had a goal disallowed.

After the impressive performance, Mourinho had said: "It's not an obligation [to sign him], it's an option, but I think the boy is earning the decision. 

"He's making an easy decision for the club to execute the option. Incredible evolution since I arrived.

"Barely played a game [before I arrived], I think he played against Red Star Belgrade and with me it was a little bit difficult to come in the first few weeks.

"But he understood what we wanted. Good learner, good kid and I think by himself he made the decision that the club is going to execute the option. That's normal, he earned it."