ON THE afternoon of January 31 a group of 20 members of the IRA's 3rd Belfast Battalion joined the crowd of several thousand following Gerry Adams, Martin McGuinness, Mitchel McLaughlin and Pat Doherty as they marched in Derry's Bogside to commemorate the 33rd anniversary of 'Bloody Sunday'.

The Sinn Fein leaders carried a banner proclaiming: 'Who sanctioned Britain's death squads?'

The Bloody Sunday event is one of the biggest in the Provisional Republican's calendar and Sinn Fein and IRA members are bussed into Derry from all over the country for the event. The Belfast men had travelled to Derry by car and coach and after the march had apparently drank in some local pubs and then had more cans on the way back to Belfast.

The demonstration was the highlight of a weekend of Sinn Fein events in Derry including a national conference of Ogra Sinn Fein for which hundreds of student party members were bussed from all over the Republic.

The events were the start of a year-long series of activities aimed at bolstering Sinn Fein's image during the centenary of the party and preparing the ground for this year's general elections in the North and forthcoming elections in the Republic.

Bloody Sunday has been a central rallying event for the Provisional Republican Movement, portrayed as the sacred moment of martyrdom when the British Army shot dead 13 protestors and marked the supposed beginning of the Provisional IRA's 'armed struggle'.

A few hours after they left Derry, however, the men of the Belfast 3rd Battalion were themselves immersed in their own bloody Sunday episode as they set about two innocent Belfast men in a frenzied knife attack that left one dead and another on the edge of death.

Robert 'Bert' McCartney, a father-of-two boys aged four and two, received the type of wounds not seen in Belfast since the terror inflicted in the mid-Seventies on innocent Catholics by the notorious loyalist assassin gang known as the Shankill Butchers. The nearest thing the butchery outside Magennis's Bar can be compared to in recent times are the ghoulish beheadings of prisoners videotaped and broadcast on the Internet by Al Qaeda and their Iraqi allies.

McCartney was cut from his navel to his breast bone with a carving knife. Then as he was held by other members of the gang his throat was repeatedly slashed, severing his jugular vein. As he lay bleeding to death on the pavement outside Magennis's Bar behind the High Court in south inner Belfast two of the IRA men jumped on his head while a third beat his prostrate body with a sewer rod.

The knifeman then turned on McCartney's friend, Brendan Devine, who was being held down by several other IRA men, and slit his throat from ear to ear. He then plunged the knife into his stomach and ripped a two-foot-long gash up to his neck. He also stabbed Devine in the side.

The gang then went back into the bar and 'meticulously' set about wiping fingerprints and whatever other forensic evidence they might have left from bars, tables and seats.

No one was allowed to leave the bar or call an ambulance for the two men lying bleeding and unconscious on the pavement outside. A passing police car eventually spotted the two, called an ambulance and gave what first aid they could administer. The two policemen had never seen injuries like these before in their lives.

Meanwhile, before the occupants of the bar spilled out on to the street and began quickly leaving they were told in no uncertain terms that if any spoke to police everyone in the bar they would be held accountable. So far, none of the drinkers there that night has come forward. Almost everyone in the bar knew what had happened. They also knew the reputations of the IRA men who had just engaged in a savage act of butchery outside the bar doors.

Most would have known the two leading IRA men involved in the attack. One is thought to have been formally the Belfast IRA's 'officer commanding' and may now hold a position on the IRA's 'General Army Headquarters'. In other words, he is one of the most senior figures in the IRA. He is a frequent visitor to Sinn Fein offices in Belfast and is known to be close to senior Sinn Fein figures. He was still in Belfast last week.

The man who, according to local people, carried out the stabbing and slashing with the carving knife is in his mid-30s and holds the position of 'adjutant' of the 3rd Battalion. He has a reputation for extreme violence including sexual violence and torture of women.

Three years ago the Catholic population of the tight-knit Markets area, close to Magennis's Bar, were horrified at an incident in which this man kicked a young pregnant woman in the stomach during an incident in which he was beating up her boyfriend. The young woman was taken to hospital but her six-month-old foetus did not survive and she had to receive emergency surgery to stop internal bleeding. There was no outcry basically because of the extent of fear instilled in the local population by this man and his associates.

Last year the same man earned himself further loathing after an incident in which he reputedly branded another young local woman with a steam iron after ripping her blouse off and pressing the iron against her breast. The victim had been trying to help her best friend who was on the floor being kicked and tortured by the IRA man.

OTHER members of the IRA who still flaunt their power over their local communities include another Markets man who raped a 15-year-old girl and another who threw his girlfriend off a balcony at their holiday hotel in Spain. The woman in Spain, who suffered multiple injuries, recovered but made no statement of complaint to local police.

After the murder and attempted murder, the knife-wielding IRA man went on the run to, it is rumoured, Dublin's northside, where he has close connections with the local IRA unit led by a man who is a fairly well-known Sinn Fein election agent as well as the main organiser of the container heists from Dublin Port.

The Belfast man and his friends were suspected of robbery of €7 million worth of cigarettes from Belfast Docks in June 2001. Four lorries were used in the massive heist and afterwards gardai recovered empty lorries and containers at Drogheda and Collon, Co Louth and at an industrial estate at Naas. The fourth lorry was discovered by the PSNI in Omagh, Co Tyrone.

Gardai believe that members of the Belfast 3rd Battalion have had close links with the Dublin IRA for several years. Several of the IRA men from Belfast have taken part in Sinn Fein election campaigns in Dublin.

The murder and horrific injuries inflicted on Brendan Devine might have been quickly forgotten and covered up by Sinn Fein where it not for the steely determination of Bert McCartney's four sisters who last week began campaigning for his killers to be brought to justice.

The outrage caused by the murder in the Short Strand and Markets also led to a candlelit vigil attended by 1,200 local people - about a third of the population of the enclave and the largest anti-IRA gathering in a nationalist area of the North since the mid-Seventies.

Sinn Fein representatives, caught in the glare of publicity generated by the sisters' stance, refused to say that witnesses should help the police investigating the murder but said they should contact someone like a priest or solicitor or even a member of the McCartney family. The sisters immediately rejected the offer saying the intimidation of witnesses should stop so they could give statements to police.

Paula McCartney, who is acting as spokeswoman for her brother's fiancee Bridgeen Hagans and the rest of the family said: "The IRA was involved in a clean-up operation in the bar so there would be no forensic evidence. The IRA threatened eye-witnesses. The IRA visited the local community centre and ordered people not to talk to the police and media - not even to talk to each other - about the murder. This raises very serious questions for Sinn Fein."

All the IRA men and Sinn Fein 'activists' in Magennis's Bar that night are well known yet three weeks after the murder not one witness had come forward even though Bert McCartney was a popular and well-thought-of member of his community.

Sources in Belfast said that despite the statements by Sinn Fein and the IRA that witnesses should not be intimidated, no one living in the Markets or Short Strand is in any doubt of what would happen if they did help the PSNI investigation.

The entire community was also well aware that while the IRA was issuing a statement under the signature of the non-existent 'P O'Neill' saying it was not involved in the murder that two of its most prominent members in Belfast - one of whom has acted as a bodyguard for Martin McGuinness - led the attack on the two men. They were also aware that while the denials were being issued, the IRA was also protecting its psychopathic 3rd Battalion leader in a safe house somewhere in Dublin.

As Sinn Fein and the IRA desperately tried to play down the murder of Robert McCartney last week - helped by docile newspaper reporting of the IRA 'denial' - the sisters vowed to take their campaign to the White House if necessary. The sisters petitioned the US Consul in Belfast, Dean Pittman who felt compelled to call on Sinn Fein to "help guarantee the safety of those who co-operate with the police". On the streets of Belfast there is seething anger but few believe the IRA is prepared to give up the "mad men" who butchered Bert McCartney.

- Jim Cusack