Southampton have completed a £11.5m move for Dutch defender Virgil van Dijk from Scottish champions Celtic. The 24-year-old has agreed a five-year contract with the Premier League club after passing a medical. Van Dijk joined Celtic in 2013 after three years with Groningen and has won two successive league titles and the Scottish Cup with the Bhoys. “Moving to the Premier League is the right time for my development,” he told Southampton’s official website.  “Southampton is the perfect step for me right now. I want to play as much as possible, get settled in quick and show everyone what I’m capable of and do well with the team.” Van Dijk said after Celtic’s Champions League play-off loss to Malmo that he was considering his Bhoys future. Meanwhile, Saints forward Emmanuel Mayuka, 24, has left to join French club Metz on a three-year deal.  The Zambia international, who was top scorer at the 2012 Africa Cup of Nations, joined Saints from Young Boys in August 2012 and scored once in 19 appearances. He spent the 2013-14 season on loan at French side Lorient.