Simon Byrne resigned with immediate effect as Chief Constable of the Police Service of Northern Ireland (PSNI) on Monday, September 4.

“The Chief Constable Simon Byrne has today tendered his resignation to the Northern Ireland Policing Board with immediate effect,” Northern Ireland Policing Board Chair Deirdre Toner said on Monday.

Toner said: “I would like to record my thanks and appreciation to Simon for his work over the course of the last four years as Chief Constable.

“He is undoubtedly a dedicated police officer with a deep respect for the profession of policing.

“He was very aware of, and greatly appreciated, the often difficult job that officers and staff across the organization do on behalf of the community.

“This may not always have been apparent to onlookers, but it was very much his modus operandi as was his desire to improve policing for the community through modernization and investment in local policing arrangements.

“His tenure was subjected to intense scrutiny, and I am sure that the last few weeks in particular have been incredibly difficult for him personally and professionally.

“The Board will now consider the leadership arrangements going forward.”

Toner shared the following statement on Byrne's behalf: “The last few days have been very difficult for all concerned.

“Regardless of the rights and wrongs, it is now time for someone new to lead this proud and resolute organization.

“Can I thank those who have shown me trust, advice, and friendship.

“And of course thank you to the brave men and women of the Police Service of Northern Ireland.”

The Northern Ireland Policing Board said on Monday that the Deputy Chief Constable, Chris Todd, will exercise all of the functions of the Chief Constable while a new Chief Constable is recruited.

Byrne's resignation comes after the PSNI suffered a major data breach in early August and was later found to have unlawfully disciplined two junior officers in 2021.

On August 8, the PSNI was rocked by an "extremely serious" data breach that saw the surname, initials, rank/grade, role, and location of all serving officers and staff posted online for up to three hours.

On August 28, Northern Ireland's High Court ruled that two junior PSNI officers were unlawfully disciplined for an arrest made during a Sean Graham's Bookmakers commemoration event on Belfast's Ormeau Road on February 5, 2021.

Justice Scoffield said he will "quash the decision made to suspend the first applicant and the decision to re-position the second applicant."

On August 31, Byrne and Todd were questioned by the Northern Ireland Policing Board about the ruling. Byrne said he accepted the High Court's ruling and that he would not be resigning.