The Belfast playwright Gary Mitchell has won the George Devine award for The Force Of Change, his controversial play about RUC collusion with loyalist terrorists.

Mitchell is the fifth playwright from Ireland to win the £8,000 award, the most prestigious theatre award for new writing, in six years.

The Guardian's theatre critic Michael Billington described the production at the Royal Court theatre in London as unmissable. "Last year, in Trust, he wrote a gripping play about the destructive impact of the Northern Irish Protestant ethic on its own children. Now in this even more nail-biting work he shows how both policing and terrorism are dominated by a boys' club atmosphere and by a series of interlocking collusions."

Mitchell, who lives in Rathcoole, the north Belfast housing estate where he was born, came to prominence three years ago with In a Little World of our Own. Seen early on as a lone voice grassroots loyalist, he has become a master of tense and complex thrillers.