Hibs sign Caldwell
The defender severed ties with Newcastle on Thursday and immediately travelled up to Edinburgh to finalise his move to Easter Road.
Caldwell had little hesitation in inking a contract which ties him to Hibs until the end of this season.
The Scot will join his new team-mates for training on Friday and is available for selection to face Dundee at the weekend.
Speaking to the club's website about signing for Hibs, Caldwell said: "I have made no secret of the fact that I love it at Easter Road, Hibernian are a good club with a great squad of young players.
"I've always said that should the opportunity arise to return here I would jump at it - the last time I was here I worked with Bobby Williamson and his coaching staff and now I'm looking forward to doing so again."
Williamson expressed delight at finally capturing a player who turned out for the club in a loan spell earlier in his career.
"Gary is a tremendous player and will be a great addition to the club," said Williamson. "I've worked with him both here at Easter Road when he was last at the club on loan, and with the Scotland Under-21 squad.
"I am delighted to have secured his signature."