Tierney will become the most expensive Scottish player in history when he pens a £75,000, five-year contract.
"He is a well known player and adds to our defensive strength".
The defender was a regular under Maurizio Sarri last term and it appeared he would again play a key role under new boss Frank Lampard. In May, shortly before he anchored Chelsea to a 4-1 Europa League final win over Arsenal, he described Emery as "a great guy, a great coach, a great person".
In further breaking news regarding Arsenal, meanwhile, as confirmed by the ever-reliable David Ornstein a short time ago, Everton have struck a deal with the capital giants over the signing of Alex Iwobi. Unai Emery was very keen to bring in the Scotsman to the Emirates for the right cost and eventually they have succeeded in clinching the deal at the third attempt. People need to know that as well. I'm delighted to be here.
He told Sky Sports: "He would be a better left-back than what Arsenal now have".
Elneny has been recently linked with a move away from North London with several European clubs reportedly showing interest in the Egyptian.
The Scotland worldwide clocked up an enormous 170 appearances in all competitions with Celtic during his short career, helping Celtic win five league titles, three Scottish Cups and three League Cups. He made his debut for the club as a 17-year-old in 2015 and has experience playing in the Champions League and Europa League from his time in Scotland.
The 25 million-pound transfer fee makes Tierney, the most expensive player to be signed from the Scottish Premiership, surpassing the 20 million pounds Olympique Lyonnais paid Celtic for centre forward Moussa Dembele past year.
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