"It's great to be back and I'm looking forward to the challenge," Defoe told Sky Sports. "It's hard to put it into words, it's brilliant.
"I've been looking forward to it all day. A number of things [made me return]. Obviously everyone knows the manager was a major factor. My family still live in London and the fans were a factor too. You can tell by the reception I got.
"I never wanted to leave, but as a professional there comes a time when you think you need to move on.
"I did in order to improve my England career, but I didn't want to go in the first place."