The 27-year old joined Southampton in 2011, and was a vital member of the squad which achieved promotion to the Premier League. Despite falling out of favour during the Saints first season back in the top flight, the Scottish international made 20 league appearances and scored one goal, in a 6-1 defeat to Arsenal.
The 2013/14 season saw chances hard to come by, with the emergence of highly rated youngster Luke Shaw limiting Fox to just three Premier League appearances - the last in a 3-2 home defeat to Tottenham in December.
From a desire to get more first team football, Fox joined Nottingham Forest in January, on a temporary deal until the end of the season. Having impressed in his 15 appearances at the City Ground, the club made no hesitation on securing his services on a free transfer.
Sky Sports reports that Fox agreed a three-year contract at the time of his loan deal, and the club have chosen to activate this clause with immediate effect.
The arrival of Fox signals the first step of a rebuilding process that will be continued when club legend Stuart Pearce officially begins his role of manager, effective from July 1.
Following a disappointing season under Billy Davies, owner Fawaz Al-Hasawi decided a change was needed. Davies was sacked on March 24, with Gary Brazil taking over as caretaker manager until the end of the season, with former club captain - and 12-year servant - Stuart Pearce officially taking the role this summer.
In an interview following the end of the Championship season, Pearce spoke of the immense pride he feels in returning to the club which loves him, and of leading them to success.
Quoted by Sky Sports, Pearce said: "Nottingham Forest getting into the Premier League under my tenure as manager would be the proudest moment of my life. That's what we're all striving to achieve.
"But then I'm acutely aware there are 20-odd other teams in the Championship with that attitude and some with real expectations a mile above where they should be.
"Football doesn't owe you a living. People who have spent a lot more money than the likes of Burnley have ended up not getting in the Premier League
"The Championship is not an easy league to get out of and you have to be. consistent over 46 games. Football doesn't owe Nottingham Forest anything because they won the European Cup a number of years ago."
Even if football does not owe Forest anything, their fans will be desperate for a return to their previous success, and it is up to Pearce to revitalise the fortunes of the former European Cup winners.