When I joined the RUC in 1970, Northern Ireland had just experienced almost two years of civil unrest, but, like many, I felt it was but another episode in the troubled history of Ireland and would soon pass. How wrong I was.

Little did I realise that 30 years of bitter violence lay ahead, which would result in almost 3,700 deaths, with thousands more injured.

I was at the coal-face of anti-terror policing during most of those terrible years and it began for me when I was posted as a probationer constable to Tennent Street in north Belfast. The station was responsible for policing the Shankill, Ardoyne and Oldpark areas.

The reality of my posting was to prove that the Troubles were far from over as, during my first two years of uniformed service, I was the first officer at the scene of 12 sectarian murders. Most of these victims had been shot, but others had been savagely beaten to death.

The faces of these unfortunates were like something from a horror movie. It was clear that the hatred some people had for each other ran much deeper than I could ever have imagined.

In late 1972, I was accepted into the CID and gradually worked my way up the ladder, ending my service as a detective superintendent and deputy head of the CID for Belfast. At that stage, I had attended approximately 100 murder scenes and had faced down some of the most notorious terrorists, ranging from Martin Meehan of the IRA to Lenny Murphy, leader of the Shankill Butcher gang. I thought I had seen and heard everything.

But I was totally unprepared for the phone call I received at home on the evening of Sunday, February 12, 1989, informing me that leading solicitor Pat Finucane had been shot dead at his home.

I had known Mr Finucane from my many days at Belfast Crown Court and while it would have been unwise for him to be seen speaking to me in the crowded foyer, occasionally I would meet him in an isolated corridor and he would give me a friendly nod.

On arriving at the scene, it was cordoned off and I was led to the kitchen of the house by the local CID duty officer, where I saw Mr Finucane lying on his back. His face was a mass of bullet holes and powder burns and this indicated that the killer had stood over him and pumped bullets into his head from a distance not greater than 18 inches.

We also noted two bullet holes in the glass kitchen door; the gunman had downed his victim by first firing two shots through the door and into Mr Finucane’s body.

Several spent 9mm cartridges littered the floor, so the likely weapon was a Browning automatic. This was undoubtedly the work of a very professional assassin from either the UFF or UVF.

Geraldine Finucane, the victim’s wife, had been shot in the foot and was in hospital, but the rest of the family had isolated themselves from us by staying in the front lounge behind a closed door.

I had the scene photographed, videotaped and expertly examined by forensic scientists, in addition to Professor Marshall, the State Pathologist, after which we placed Mr Finucane in a body-bag and had him removed to the mortuary.

I then went to the nearby Antrim Road RUC station, where I summoned extra detectives to work on the case and set up an incident room.

Many observers have written about the case and I am correctly presented as the senior investigating officer, but this was just another killing to add to the list of murder investigations then under supervision by me.

However, I did realise that the murder of Mr Finucane was causing a political storm and hitting the news headlines worldwide, so, in reality, I dedicated myself more to his case.

Two days after the murder, I was surprised to receive a phone call from RUC HQ, advising me that the head of the CID for Northern Ireland, Assistant Chief Constable Wilfred Monahan, was on his way to visit the Finucane incident room. He stayed for about 15 minutes and I saw him back down to his car.

Before getting in, he turned to me and said, “Alan, if I were you, I wouldn’t get too deeply involved in this one.” He then closed his car door and was driven off.

I was quite stunned by his advice and not a little confused. Was he saying I had a lot of murders on my hands and Mr Finucane was a republican sympathiser unworthy of too much police time? Or was there some deeper meaning?

I returned to the incident room and continued with the investigation full steam ahead, but the following day I received another unexpected visitor from RUC HQ in the form of a Special Branch detective chief superintendent, who was deputy head of Special Branch for Northern Ireland. I thought he was going to offer me some vital information, but I simply briefed him and he left.

Almost from the moment I arrived at the scene of the murder of Pat Finucane, I sensed that there was a great deal of hostility towards the RUC from the family. I wasn’t in the least surprised as it was widely known they held strong republican views.

However, as the days wore on, the Press began to report that the family suspected some form of state involvement in the killing. It was not an idea that I took onboard easily, as I didn’t believe any state agency would be so stupid as to arrange such a killing. The ramifications for that, if true, would be disastrous and far-reaching.

My investigation ran for about six weeks and, as with so many other cases, it had to be shelved until some new information came to light.

The next significant event for me in the Pat Finucane case was the inquest into his killing, which was heard in September 1990. I was the sole police officer in attendance and, as anticipated, the courtroom was filled with members of the Finucane family and representatives from the world’s media.

After the formal evidence had been presented, such as the post-mortem examination report, I was called to the witness stand.

Junior barrister Seamus Treacy (now Lord Justice Treacy) represented the Finucane family. He cross-examined me at length and there was undoubtedly a suggestion of collusion in his questions.

I fielded his examination as best I could, but more in the interests of the reputation of the RUC, as by then I had a distinct unease about the whole case.

In short, I had a nagging feeling that there had, indeed, been dirty work afoot by the intelligence services.

I was starting to believe that I had given them too much credit by believing they would not be so stupid as to murder Pat Finucane by proxy — ie using a loyalist terror gang to carry out their dirty work.

The following year, the case was cracked wide open by two of the best detectives I had ever worked with: Detective Sergeant Johnston Brown and Detective Constable Trevor McIlwrath.

A well-known UFF assassin, Ken Barrett, had approached them, offering to give evidence and they had cleverly pulled him onto the punch by getting him to boast about his killings. These included the murder of Pat Finucane.

In due course, Barrett was convicted of the murder and sentenced to life imprisonment, but under the terms of the Good Friday Agreement he served only two years.

It was also established that UFF man William Stobie had provided the weapons for the murder. He was shot dead by the organisation, as they feared he would give evidence against them. A third man involved in the killing hanged himself from the goalposts of Glencairn playing fields.

One of the many things that stick in my mind from the Finucane case is that a close colleague told me it was a case that would follow me to my grave.

I don’t believe we’ve heard the last of it yet.

** Retired RUC Detective Superintendent Alan Simpson is the author of Duplicity and Deception (Brandon Books)