The England Under-21 international has joined the League One side on-loan from Norwich until the end of the season and Westley showed his delight at getting his man.
"Dec was first recommended to me during the summer, I was away doing my pro-licence and one of the FA coaches mentioned him to me," he told the club's official website.
"He said if you want a top kid who needs to go out and get games and served his apprenticeship and has done well at every level he has played at, he is the player for you.
"Everyone from the youth coaches to Stuart Pearce in the U21s has spoken very highly of him so I have had a good look at him and I have been speaking to Norwich about him throughout the season and he became available and has joined us until the end of the season.
"It is nice to bring a goalkeeper of his qualities into the club and it is a nice boost following the departure of Steve Simonsen."