O’Neill said: “Shaun was out of contract in the summer, and we left it late before we even went in for him because I honestly thought he would sign a new contract at Celtic.
“But we were very encouraged with the way things progressed once we knew Shaun wanted to come and sign. We agreed everything with Celtic, and then it was simply a race against time – which we managed to win thankfully.
“He is a very decent player – not only during my time with him at Celtic – and he has done excellently in the last couple of seasons and has featured for Scotland.
“Shaun is an excellent player, and I think he is as conscientious as they come. He will be a big asset to this club, I have no doubts about that.”