He told the Palace website: "I wanted to stay at the top level, which is obviously the Premier League.
"I heard of Crystal Palace's interest from January actually, and once they got promoted Ollie gave me a call when I was away on holiday.
"We had a good talk for about 45 minutes and after that conversation there wasn't much doubt in my mind where I wanted to go.
"Ollie's the main factor, but obviously there's a lot of talent here and him and the chairman are planning on bringing in more. It shows what their goals are and I'm definitely looking forward to it."
"I hope I can bring a lot to the team. I've got experience of the Premier League and the gaffer's going to give me the freedom to play how I want to play - my attacking game."