Campbell signed a six-month deal with the Gunners in January.
“I’ve always believed in my own ability, but never thought I’d play for Arsenal again,” Campbell told The Times.
“I came back to try and keep fit, with a view to getting another club, in the Premier League or the Championship. I trained by myself for three weeks, which was hard work mentally. I tried to do everything – jogs, sprints, in and out of cones, I went swimming, anything just trying to get the best out of the facilities I had. Ball work was pretty difficult on my own!
“I started training with the first team after about a month, just popping in to help out if they were a few bodies light. I was the spare man, but didn’t mind. It was like going back to school, but I didn’t mind starting again.
“I never gave a single thought about playing for Arsenal until January, when Arsene Wenger started to consider it. It was a gradual process. He never said, ‘we’re short Saturday, can you play?’ Not quite anyway.
“The boss saw me training, making better times, playing okay and how I was conducting myself around the club. He said he was thinking about signing players, but they were a bit top-heavy with defenders so I’d have to wait.”
Campbell added: “I had a few other offers, but once this one came along there was only one winner.
“Everyone else was blown out of the water. There were a few things to sort out as they had a few defenders, but I said to the boss, ‘However long you want me to wait, I’ll wait’. He was honest and said he wouldn’t stand in my way if a move came up, but I was prepared to wait. I don’t mind being patient.”
“I think I can keep myself fit and play top football for the next two to three years,” he added.
“This season and at least another two. I’m here for six months, and if something happens, something happens.
“If not I’ll have to look elsewhere. The manager’s told me I’ve got to the end of the season and he’s looking for other players, but I want to play as many games as possible for Arsenal and help them to win something.”