The striker travelled to Spain earlier this week for talks with the club and has now completed the formalities of the switch.

It's the second loan spell of Braithwaite's short Boro career with the player spending the second half of last season on loan at Bordeaux. 

Braithwaite, who was signed from Toulouse in the summer of 2017, joins a club who are 16th in the Spanish top-flight.

Speaking after Tuesday's game at Derby, Boro boss Tony Pulis confirmed the move was imminent: "Braithwaite is talking to Leganes. The club who were interested in him in the summer. We think that will happen.

“I have not had a lot of time with him, I had two or three weeks before he went last season on loan, and four or five months this season. Good luck if he wants to go. He wanted to go in the summer. He has got his move now.”