The former Republic of Ireland centre-back, who possesses a wealth of Football League experience with the likes of Preston North End, Leicester City and Peterborough United, recently linked up with the Lions after a spell with relegation rivals Solihull Moors.
Cox, who has also brought in loan defender Harry Flowers from Burnley – who could also make his debut at Dover tomorrow – feels that St Ledger, 33, will add some defined leadership and experience into a back four which has conceded several costly late goals this term.
On St Ledger, who suffered an injury scare with his shoulder last weekend, although thankfully the problem has now cleared up, Cox said: “We got to hear about him and invited him in for a couple of days training.
“The reason behind Sean is that, especially after the period after the FA Cup when the results were a bit erratic, we felt that we needed, not just more leaders on the pitch, but a know-how.
“We wanted somebody to help the younger players in terms of their decision-making, especially at certain periods of the game. We have also conceded a lot of late goals of late; goals that have not been crafted or well-created.
“A little bit more experience on the pitch could have probably cured it. Sean comes with a wealth of experience and know-how and that is something we were keen to add to the squad.
“You look at the goals that are conceded at this level, and a decent percentage are mistakes. It is having that somebody with the positional sense and, more importantly, that experience to pull others along and have that calming experience. We know Sean will bring that.”
And on the addition of Flowers, the Lions chief added: “I have been speaking to Burnley for a number of months. Even when I was at my old club [Barrow], I had my eyes on Harry.
“We took Jimmy Dunne at that stage and they [Burnley] could see the progression that he made as he is now in the Football League and Harry comes very highly rated and they look at it with him as having a very good future in the game too.
“He is someone who we know that we have to work with, regarding certain aspects. But he comes with very good ingredients already within him. He is another positive signing.”
Cox is also working towards drafting in a goalkeeping replacement for Jonny Maxted ahead of the weekend and says that the club could not stand in the keeper’s way after he made it clear that he wanted to test himself in the Football League with Accrington.
Cox added: “With Maxy going, that left a big hole.
“But he had four months left on his contract. And the deal for the football club was very good.
“Having spoken to Maxy, he is a very honest boy and has been a brilliant professional for the club. But he wanted to go into the Football League.
“Whether it was now that we got a transfer fee for him, or we did it in the summer, Maxy, at some point, was going to go to Accrington. It was a good business deal for the football and Maxy, who has been superb for us this season.”
FC Halifax, in 17th place, head to play-off chasing Bromley tomrorow.