Brighton and Hove Albion 1 Newcastle United 2: Perez claims HUGE win at the Amex Stadium
Rafa Benitez's side, trailing to a controversial first-half penalty from Glenn Murray, looked to be heading for a defeat at the Amex Stadium.
But Diame diverted a Christian Atsu shot past David Stockdale nine minutes from time.
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Hide AdAnd substitute Perez scored late in the game to claim all three points for the visitors.
The result saw Newcastle return to the top of the Championship ahead of Saturday evening's game against third-placed Huddersfield Town.
Referee Robert Madley penalised Ciaran Clark for what he felt was a foul on Murray as a corner was delivered into the box. The decision looked harsh.
Murray stepped up to take the resulting penalty, and Newcastle lacked ideas and inspiration before the break.
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Hide AdBut a dramatic late turnaround saw them score two goals in the last 10 minutes.
A shot from Atsu struck Diame on its way past Stockdale.
And Perez beat Stockdale with a simple finish after Atsu, having run on to a long ball forward from Matt Ritchie, squared the ball for him.
BRIGHTON AND HOVE ALBION: Stockdale, Saltor, Dunk, Stephens, Baldock (Kayal, 82). Knockaert (March, 87), Pocognoli (Tomori, 18), Sidwell, Murphy, Murray, Duffy. Subs not used: Walton, Huenemeier, Hemed, Akpom.
NEWCASTLE UNITED: Darlow; Yedlin, Lascelles, Clark, Dummett; Shelvey, Colback (Murphy, 74); Ritchie, Diame, Atsu; Gouffran (Perez, 82). Subs not used: Elliot, Hanley, Anita, Gamez, Mitrovic.
Goal: Murray 14 (pen), Diame 81, Perez 89
Bookings: Yedlin 36, Knockaert 37, Duffy 58, Murray 90
Referee: Robert Madley (West Yorkshire)
Attendance: 30,230