The left-back became Steve Bruce’s third signing of a busy week – fifth of the summer as a whole – following on from Callum Wilson and Ryan Fraser’s confirmation on Monday. The Magpies brought in free transfers Jeff Hendrick and Mark Gillespie earlier in the window.
And the 22-year-old Northern Ireland international has been reacting to the move on Twitter.
He said: “HOWAY THE LADS ! Delighted to have signed with this great football club ready to go.”
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Speaking to NUFC TV he added: “It was a little bit unexpected but something I was obviously looking forward to when I heard that there was serious interest. I'm delighted to be here.
"Newcastle's such a great club with such history. I knew it was an opportunity I would love to take with both hands."