NATHAN Ake admits joining Cherries will present him with "an exciting challenge".

He told the club website: “I had a great time here last season so I’m really happy to be back.

“It’s an exciting challenge. Chelsea is a great club and I learned so much there but this is a new step and the right place for me to develop even more.

“The fans haven’t seen the best of me yet. I always set the bar high so I know there is a lot of things I still have to work on.

“With the help of the manager here I know I can keep improving and become a better player.”

Cherries bossr Eddie Howe said: “I am delighted that we have completed the signing of Nathan on a permanent basis.

“He is someone we know all about, having had a very successful loan spell here last season.

“Nathan is an outstanding young player with a fantastic attitude and a great desire to learn and develop.

“He has a very bright future ahead of him and I’m very pleased to say that future is here.”

And chief executive Neill Blake added: “Nathan may have only been with us for a short time last season but he was a big part of what we achieved and made a huge impression on everyone, both on and off the pitch.

“We were determined to bring him to the club permanently and I am delighted to secure the services of a young, hungry, talented, international defender.

“Having already signed Asmir Begovic and Jermain Defoe this summer, this is another statement of our intent and another player who will help drive the club forward.”