Cranie, 20, was out of contract at Southampton and had refused the offer of a new deal to stay at the club.

Pompey will have to pay a compensation fee to Championship side Saints as the player is under the age of 23.

Cranie told BBC Radio Solent: "I didn't really think about the rivalry between the two clubs, I just wanted to come down here at play football."

He added: "I'm very happy to be back in the Premiership. I've been down in the Championship for a couple of seasons now, but to get back to the top flight, it's a pretty big step for my career.

"Harry Redknapp was the manager who gave me my chance in the Premiership when he was at Southampton, so he was a big part in my decision to move here."