THEY gathered at about three o'clock on that fine sunny afternoon on the open green beside St Mary's Church on the Creggan estate. They were in carnival mood, Lord Widgery noted at the subsequent tribunal. What he failed to note was the purpose of the protest there was nothing festive about that.

For six months, more than 790 Catholic men had been imprisoned across the North without charge, without trial, without a release date. Internment was Stormont's convulsive last gasp.

In the seven months up to its introduction in August 1970, 28 people had died violently in the six months that followed, that figure had soared to 177. Derry in January 1972 was a deeply disturbed city wracked by unrest civil disobedience and agitation about civil rights and internment. Parades and processions had been banned by law since internment day. Still, the prevailing spirit in Creggan that Sunday in January 1972 was good humoured.

Legal or not, marches like this were a family affair; a few children playing tag through the crowds, neighbours strolling along together, boys arranging to meet girlfriends at points along the way.

Depending on who was counting, they numbered "something between 3,000 and 5,000" (Widgery), upwards of 10,000 (The Irish Times), or even 20,000 (individual estimates). Among them was 26 year old William McKinney, a newspaper compositor and the eldest of 10 children. His young brother, John, had pleaded to go with him, but Willie and his mother said No, there might be "bother". So John watched Willie leave the house, armed as always with his cine camera, watched him until he could not see him any more ...

Soon after three, the parade moved off led by a lorry carrying a Civil Rights Association banner and some of the organisers. Their destination was Guildhall Square via the Bogside and William Street. At one point the parade was halted while the stewards and others pleaded with several hundred youths to throw away their sticks and bottles.

The march stretched to about 500 yards as they entered the heart of the Bogside through Lecky Road, singing We Shall Overcome and shouting anti internment slogans. Unable to take the obvious route through Rossville Street - blocked by a low rubble barricade - they veered left up Westland Street.

Among those eyeing the marchers were troops of the 1st Battalion of the Parachute Regiment - known as 1 Para, the roughest, toughest unit in Northern Ireland.

Officially, their orders that day were to act as an arrest force, "to conduct a scoop up operation of as many hooligans and rioters as possible". After entering the west end of William Street, the organisers on the lorry spotted an army barrier with two Saracen personnel carriers and riot equipped soldiers blocking the route further down William Street. Instead of driving straight down William Street and into a head on confrontation, they turned the lorry right into Rossville Street.

Many of them had no idea why the lorry had left the planned route. Eventually, many were persuaded by stewards to follow it, but many stayed on course for the cul de sac created by the army barrier down William Street.

As the crowd built up at the barrier, stones were hurled at the troops; "by riot standards, not particularly heavy," said press reports; "stone throwing on a very violent scale," according to Widgery.

A water cannon was called up and men, women and children were crushed into doorways as the vehicle drove at the still tightly packed throng, spraying them with a jet of purple dye. Further stone throwing episodes at nearby barricades were eventually curtailed by large concentrations of tear gas which forced people back into Rossville Street.

By 4 p.m., Widgery concedes, the march had been "contained" and any remaining rioters around William Street "could have been dispersed without difficulty". At 4.07 p.m., 1 Para - under the command of an officer who later claimed not even to have had a view of the area - was ordered forward in the face of a large mixed crowd that, according to Widgery, included rioters, marchers, local residents, reporters and sightseers chatting in groups on the waste ground in Rossville Street.

WHAT then ensued, according to contemporary Irish Times reports, was "a para troop invasion ... carried outwith split second timing and at such bewildering speed as to make it very evident that a well rehearsed plan was acted out that day".

At the signal, at least eight Saracens and two Ferret armoured cars raced into action along Rossville Street and two parallel streets into the Bogside. At the same time, several paratroop marksmen opened covering fire and advanced up Rossville Street towards people clustered at the rubble barricade.

It took no more than 20 minutes to kill 13 people and to injure another 13 (one of whom would die of his wounds a few months later). Six of the dead were only 17 years old. One of these, John Duddy, was probably the first to die on Bloody Sunday, shot while running from soldiers in the courtyard of Rossville Flats. His killer was never identified. In fact, of those six dead boys Widgery succeeded in identifying only two of the perpetrators.

The killer of Willie McKinney was never positively identified either. Eyewitnesses reported that he was shot with his hands in the air.

The casualties were not confined to men of military age, as stated by the army. Mrs Peggy Derry, a widowed mother of 14 children, was transferred to a Belfast hospital for emergency surgery after a bullet passed through her groin.

An Italian journalist, Fulvio Grimaldi, saw a young man who was wounded crouching against a wall: "He was shouting `Don't shoot, don't shoot'. A paratrooper approached and shot him from about one yard." A young man who raised his hands too quickly was shot dead at point blank range.

Twenty years later Father Edward Daly, a priest who assisted the wounded and dying that day and later became Bishop of Derry, told The Irish Times: "They were all single shots. It was very discriminate, each target was picked out and killed ... It was done over a period of 15 minutes. It wasn't an instantaneous thing. I think that gave it a particular kind of sinister dimension".

Amid this murderous rout, tales of heroism abounded, such as that of the 10 to 15 young men who moved out of cover with their hands high in the air to reach crumpled bodies lying on the cobblestones of Glenfada Park.

As dusk fell on the city, an Irish Times reporter, Dick Grogan, tuned in to the army waveband to hear a crisp voice report: "There are two photographers at Rossville Street flats taking photos of the civil rights banner covered in blood". It seemed to summarise perfectly the terrible poignancy of Derry's tragedy.

THAT night, the shattered residents of the Bogside gathered around their televisions to watch the British news bulletins. They heard the BBC report that the troops entering the Bogside were met "in an obviously calculated move" with "a fusillade of fire".

They heard the commander of the British land forces in the North, Maj Gen Robert Ford, state baldly that the troops had fired only at bombers and snipers: his men, he claimed, had been met with nail bombs, petrol bombs, acid bombs and a hail of bullets.

The Daily Telegraph concluded that the troops had "no option" but to shoot, while the Daily Mail blamed the "irresponsible leaders" of the protest.

Independent observers such as journalists Simon Winchester from the Guardian and Fulvio Grimaldi immediately and flatly rejected any allegations of provocation by the marchers. Ivan Cooper MP was unequivocal: "The British army murdered people in this city today".

As the North shut down, the news of the killings fell like a hammer blow on the South. By night fall, an independent public inquiry had already been demanded by Cardinal Conway, Dr Farren, the Bishop of Derry, and Dr Conor Cruise O'Brien, the Labour party spokesman on foreign affairs.

The next day unwound like a slow motion horror movie as history and mythology converged to affirm and validate long repressed prejudices. But the burning anger was palpable. Many thousands of workers and students either stayed away from factories, offices, shops, schools and universities or walked out spontaneously to join mass meetings and protest marches through the streets.

In Dublin men, women and children marched to the British embassy in Merrion Square where, at one point, about 5,000 gathered to chant slogans and, in violent scenes, threw petrol bombs, bricks, bottles and stones, smashing windows and starting a fire.

Around the State, towns closed down for public protest marches. In Galway and Limerick, dockers refused to work British ships and oil company workers at Shannon refused services to all British aircraft. The Union Jack was burned on the streets of Cork city.

The Cabinet met in emergency session and the Irish Ambassador in London was recalled. In the British House of Commons, Bernadette Devlin, the young independent MP for Mid Ulster, who had prostrated herself before a hail of bullets in the Bogside the previous day, rushed across the floor and struck the Home Secretary, Reginald Maudling, several times across the face, describing him as "that murdering hypocrite".

That night the Taoiseach, Jack Lynch, addressed the nation, announcing that the Dail would vote finance to help all movements "who were working peacefully to obtain freedom from unionism". He also declared Wednesday a national day of mourning.

On Tuesday two bomb explosions destroyed the Royal Liver Society branch office in Dun Laoghaire and blew a door out of the British embassy where 7,000 people had converged.

In Waterford the destruction of the docks office in an explosion was greeted with jubilation by the port workers.

Meanwhile, in Britain the Minister of State at Defence was still insisting that the army had conducted itself "with great skill and great restraint" and the Prime Minister, Mr Heath, announced that the British Lord Chief Justice, Lord Widgery, would conduct the inquiry into the Derry killings.

As Derry buried its dead on Wednesday, the British embassy finally succumbed to its fate. Fire consumed it in the afternoon, and Dr David Thornley told the Dail the following day that he had been there and could not find it in his heart to condemn those who threw the petrol bombs.

The national day of mourning triggered a shutdown, ranging from two hours (in the case of Aer Lingus aircraft around the world) to the entire day. Scores of demonstrations culminated in the biggest protest march seen in the Republic for a generation.

For the second day, no British aircraft landed at Dublin, Cork or Shannon airports. Newspapers published pages of advertisements from companies announcing their closure for the day. Many of these made reference to our "fellow Irishmen". One referred to "thirteen civilians slain in the City of Derry by occupation soldiery".

EXACTLY a week after Bloody Sunday, as reports trickled in of mass demonstrations in Australia, the US and Britain, more than 50,000 people took part in a silent, peaceful march on the outskirts of Newry.

It was hailed "as a catastrophic defeat for the British army" by Tom Driberg, the British Labour MP who was there. But 25 years on, as Dick Grogan writes, Bloody Sunday remains an open wound. It would be untrue to suggest that all the relatives have meekly followed the Sinn Fein line.

On the 20th anniversary, for example, Mairead McKinney, whose father Gerry was a Bloody Sunday victim, told The Irish Times that the family was incensed that Gerry Adams had been invited to speak at the commemoration rally.

"He's got a nerve to stand up there and preach and talk about the British government and what they did, trampled all over the people's civil rights and came in and shot all those innocent civilians. But he hasn't got the right to say that ... he's standing up for the IRA and they are doing exactly the same thing, so what right have they got?"

The only people the family supported, she said, were those seeking to reverse the Widgery tribunal. They simply wanted the victims names to be officially cleared.