Sporting have released a statement and then I'll take a guess at events leading up to the signing, but first let's read the Sporting statement.
"Sporting Clube de Portugal announces that during [July] the club started negotiations with Eric Dier over the renewal of his contract.
"Unexpectedly, Sporting, SAD was confronted by the player's father and official representative with a bid from Tottenham Hotspur, with that bid activating a clause agreed by previous boards of directors for the sale of the player for an amount of €5million or more, unless the personal terms offered as part of the bid are matched.
"Due to the club's current salary policy, the respective balance within the squad and the on-going financial restructuring underway at the club, it was not possible to match the proposed terms.
"Furthermore, Sporting, SAD was also informed that the player did not want to remain with the club even on equal terms and that any equal or improved personal terms would not have been accepted.
"In light of the above, Sporting, SAD announces the complete sale of the economic rights of the player Eric Dier to Tottenham Hotspur for €5milion, without any future rights relative to the player.
"Despite the above mentioned events, Sporting, SAD wishes Eric Dier all the best in his career."Eric Dier has been turning contract offers don at Sporting for 2 years so quite where the 'unexpected' element comes in I'm not sure. An agent know a players contract, he negotiates it so when it comes to moving his client on, and Eric Dier has a desire to play Premier League football, then he arranges the best deal for his client.
If he knows of a clause that states how much a player can be sold for he is going to tell the buying club. If he knows specific salary clauses he is going to tell them.
The search for youth talent continues with Lazar signing
No debut for McGee with no tour
It's bye bye Benny now
Veljkovic & Dier the future Spurs centre-back pairing
Celtic + Dagenham & Redbridge who plays in which game?
Beckham opportunity offers opportunity to Spurs
Club vs Player
Does Tom Carroll have a Spurs future
Sporting have been trying to insert a clause in a new contract for Dier that included a £38.02 million buyout clause. Naturally with his desire to play in the Premier League he was never going to sign and new contract and turned at least 2 offers down.
It doesn't take much of an educated guess to know Tottenham representatives have spoken to him over the last 2 years and let him know we wished to purchase him. If he has agreed with that move then it's possible he has been left with Sporting to develop and only now activated the clause in his contract.
Had he been purchased earlier then he would have been in the Development Squad or out on loan in the lower league, better to leave him at Sporting.
Whether that has happened here or not I have no idea but football is a murky world and it wouldn't surprise me at all if this deal were agreed with the player and his agent 2 years ago.