An investigation by an external police force into an incident linked to Northern Ireland’s Police Ombudsman has proved “significantly more complex” than first expected, a senior commander has said.

West Midlands Police are examining events related to an incident at a property linked to Ombudsman Marie Anderson in Holywood, Co Down, last September.

Police Service of Northern Ireland officers attended the address at around 6.30pm on Saturday September 23 after a report of a domestic incident.

A man was arrested as part of the inquiries and later released pending a report to prosecutors. A file was subsequently sent to the Public Prosecution Service.

West Midlands Police were tasked to investigate further aspects of the incident.

In June the Stormont Assembly was told that Ms Anderson had taken a leave of absence from work due to ill health.

At the monthly meeting of the NI Policing Board in Belfast on Thursday, DUP member Trevor Clarke asked for an update on the progress of the West Midlands probe as he expressed concern at the time it was taking.

Chief Constable Jon Boutcher said it had taken “far longer than any of us had anticipated”.

“Just to remind people we were very clear around ensuring the independence of that particular investigation because of the obvious conflict (of interest), and it’s the independence of the investigation that is the pillar of ensuring that this is being done properly, by the way,” he said.

Mr Boutcher asked Temporary Deputy Chief Constable Chris Todd to provide a fuller update.

Mr Todd told board members: “The privacy rights of everybody involved need to be respected and it is an ongoing investigation, but because the time has passed I am aware of growing interest and questions from the media, freedom of information requests, etc (and) there’s a danger that if we don’t give some assurance around the effectiveness of the investigation that speculation will grow.

“So, for that reason, I will be brief and purposeful in what I do say in response to the question and that is to highlight that it is an independently led investigation being conducted by colleagues from West Midlands Police and is ongoing.

“I continue to provide strategic support and oversight to the investigation and I am satisfied that the investigation is significantly more complex than was first anticipated, but is progressing professionally and effectively.

Chief Constable Jon Boutcher (right) and Temporary Deputy Chief Constable Chris Todd (Liam McBurney/PA)

“The investigation has two principal strands. A file has been submitted to the Public Prosecution Service in relation to the first strand and the decision is awaited.

“The second strand of the investigation is unlikely to progress further before September for reasons that are beyond the control of the Police Service of Northern Ireland or the independently led investigation team and the SIO (senior investigating officer).

“As gold commander for this, I have commissioned independent scrutiny of my own role, the strategy that’s been adopted and the objectives that have been set for the senior investigating officer and consequently, through that process, I’m satisfied that practical independence is being professionally maintained and the investigation is progressing effectively under what can only be described as challenging circumstances beyond the control of PSNI and the SIO.

“All the relevant stakeholders, importantly, have been kept appropriately informed throughout this.

“I should say again that the privacy rights of those affected must be upheld and as the investigation remains ongoing I can’t give any further detail at this time.”

A spokesman for the NI Police Ombudsman’s office said: “We are aware of the statement to the Policing Board today. However, given that the investigation is ongoing, it would be inappropriate to comment.

“We can confirm that the Police Ombudsman remains absent due to illness.

“In the Ombudsman’s absence, her functions have been delegated to senior members of staff.”