Kieran Tierney becomes the most expensive Scottish player of all time as he completes move to Arsenal

Arsenal have signed defender Kieran Tierney from Celtic on a long-term deal.

The Scotland international, 22, has joined from the Scottish champions for a fee of £25million.

The left-back, who will wear the number three shirt, passed a medical in London on Thursday and could make his debut against Newcastle on Sunday.

Manager Unai Emery said: "We're delighted Kieran is joining us. He's a very talented player who will continue to improve.

"He increases our options defensively and I look forward to him joining our group."

Tierney, who has won 12 caps for Scotland, made over 150 appearances for Celtic after making his debut in 2014.

He becomes the club's fifth summer signing following the arrivals of Nicolas Pepe, Dani Ceballos, William Saliba and Gabriel Martinelli.

The Gunners are hoping that is not the end of their business as they try and finalise a deal for Chelsea defender David Luiz.