Spurs manager Mauricio Pochettino confirmed shortly after Christmas that it was the club's intention to extend the deal and Alderweireld will now be unable to leave as a free agent at the end of this season or formally discuss his future with overseas sides, as had been the case.
The Club can confirm that we have activated the option to extend @AlderweireldTob’s contract until 2020.— Tottenham Hotspur (@SpursOfficial) January 4, 2019
However, the extension does bring a much talked about release clause to the table.
It is believed that the clause will become active in the summer transfer window, allowing any club to bypass negotiations with Spurs if they agree to meet the £25m figure.
Option taken up.— Kristof Terreur (@HLNinEngeland) January 4, 2019
“The player shall be permitted to leave the Club during the transfer window immediately following the exercising of the option, provided that his transfer is completed at least 14 days prior to the close of the summer transfer window, for a fee of £25m.”#thfc pic.twitter.com/4jQHYoII4y
Alderweireld's initial move to Spurs in 2015 was against a backdrop of controversy. He had spent the previous season on loan with Southampton and the Saints reportedly had a £6.8m option to make the deal permanent, only for parent club Atletico Madrid to cancel the clause and sell to the highest bidder on the open market instead. Tottenham won the auction at £11.5m.
Alderweireld has established himself as one of the best defenders in the Premier League during his four-and-a-half years in England. He missed much of last season due to injury but has returned to regular action for Spurs in 2018/19.
The 29-year-old has been heavily linked with Manchester United.