​​Arsenal have officially confirmed the signing of Greek international centre-back Sokratis Papastathopoulos from Borussia Dortmund in a deal believed to be worth £17.6m.

Sokratis, who is now one of a handful of Arsenal signings since long serving manager Arsene Wenger left the club in May, has signed a 'long-term' contract with the Gunners that promises to keep him at the Emirates Stadium until well into his 30s.

Initial details from the club were sparse - perhaps surprisingly, given how long they've had to prepare the announcement - not even disclosing the exact length of the contract. It has been confirmed, however, that Sokratis will wear the Gunners' number five shirt.

Sokratis' arrival is the work of head of recruitment Sven Mislintat, who has already helped bring former ​Dortmund players Henrikh Mkhitaryan and Pierre-Emerick Aubameyang to the club.

Together with chief executive Ivan Gazidis and head of football relations Raul Sanllehi, Mislintat is part of the triumvirate running the new Arsenal behind the scenes following major behind-the-scenes restructuring, with Unai Emery filling the front of house role as head coach.​​

Full-back Stephan Lichtsteiner and goalkeeper ​Bernd Leno had already joined, while Sampdoria midfielder Lucas Torreira is expected to follow in due course.