Andrew Davies has completed his £1m move from Middlesbrough in time to return to the Saints defence against Scunthorpe.
Davies's three-month loan from Middlesbrough expired on New Year's Day but George Burley is delighted to make the central defender's move permanent.
The Saints boss said: "We've lost some excellent young players in the last year or so so it's important for the club we build for the future and Andrew is a top defender.
"He wants to defend, which is difficult to find in this day and age, and he reads the game very well.
"In the short time he's been here he's got better and better.
"He's played as a left-sided centre half and adapted and has great spring - he's very good in the air and brave in both boxes.
"He's also a very good trainer, he wants to do things well and work at his game and improve so he's a great acquisition."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article