The 21-year-old has penned a four-year contract, worth just over £4million, which will come as relief for Boro manager Gareth Southgate.

"I'm very pleased that we've been able to bring Didier into the club," Southgate told the club's official website.

"As with (Marvin) Emnes, he is another exciting young talent who fits the profile of young, hungry and ambitious players that we want here.

long time

"Didier has played for France at every level up to under-21 and will really add to the competitive nature of our squad. He is a holding midfielder, who is a good athlete and a strong tackler.

"We've had our eye on him for quite a long time as we had looked at him and been impressed when watching him play for Paris St Germain and for the French national sides."

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