Middlesbrough are confident that even a last-gasp legal challenge by AZ Alkmaar, who insisted they had a pre-contract agreement with the then Heerenveen star, cannot affect their ownership of Afonso Alves.

Manager Gareth Southgate said: "The only thing that can happen is that AZ could have a claims against Heerenveen and possibly against the player as an individual.

"We will have to support him through that, but there's nothing that can affect him being registered as our player.

"We have got international clearance from the Dutch FA, so as far as they are concerned, that's done - he is registered with us and with the Premier League.

"Everything else is a sideshow, really."

Boro have been tracking Alves for some time, but finally made their move early in the January transfer window.

However, the transfer proved hugely complicated with AZ adamant they had a deal with the player despite his insistence he was going to Boro.

The Dutch FA eventually ruled in the Teessiders' favour, although confusion still surrounds Alkmaar's position.

Boro managed to push home their interest with just hours of the window remaining, and while the fee they agreed to pay after days of negotiations remains undisclosed, it is in excess of the then record £8.15million they handed over to Empoli for Massimo Maccarone during the summer of 2002.