The planned civil rights march from Duke Street in Derry to the city centre on Saturday, October 5th, 1968, and the police riot which brutally dispersed it before it could begin, have some justification to be taken as the birth of the latest phase of Ireland's "Troubles".
There had been a new politics in gestation for some years before 1968 in the activities of organisations such as the Campaign for Social Justice, the Northern Ireland Labour Party and the Northern Ireland Civil Rights Association.
The added ingredient which came with October 5th was violence, first by the police then by both police and people. More importantly, it was violence in the full view of television cameras. Images of the batoning in Duke Street of Gerry Fitt MP and the frenzied behaviour of RUC District Inspector Ross McGimpsey, laying into all around him with his blackthorn stick, shocked British viewers and permanently affected the British public's perception of the nature of Northern Ireland society.
Trouble might have been expected at the march. The route from Duke Street to the Diamond was through a predominantly Protestant area.
In any event, the local Apprentice Boys having announced their intention also to hold a parade - at the same time and over the same route - the Stormont home affairs minister, Bill Craig, intervened to ban all marches.
On the day, I was about 100 yards back from the front line of marchers when the RUC launched its attack. Like most but not all of those around me, I took off rapidly in the opposite direction. On returning to the scene about 20 minutes later I had my only confrontation with the police.
A friend and I were helping a disabled man who was in some distress. Getting him to safety involved passing through police lines. They told us roughly we had "no f***ing business being here anyway" but we were not otherwise molested. We were luckier than most.
That night there were riots in William Street and Rossville Street on the edge of the Bogside. In front of Rossville Street flats some comrades from the Revolutionary Socialist Movement were urging a march on the Guildhall, the seat of the reactionary civil power and thus perceived as Derry's Winter Palace.
At the corner of Little James's Street a crowd was throwing brick after brick at the thick glass of a baker's shop window, their aim the liberation of a multi-tiered wedding cake. A few days later Eamonn McCann told us, not for the last time, that workingclass people were angry. To me it seemed they were having the time of their lives.
Over the succeeding weeks and months there were more marches, more speeches, more riots. For a 17-year-old political junkie soaking up the rhetoric, the wit and camaraderie, the burst of violence observed from a discreet distance, it was the best of times.
For those living in mixed areas there were, of course, problems. A school friend appeared on the front pages of all the papers, being batoned to the ground by a grimacing RUC officer. What, his newsagent father wanted to know, were his Protestant customers going to think?
Our own neighbour Nancy, having spotted me on a march, querulously asked my mother: "What do they want anyway?" My mother, who hadn't a nationalist bone in her body, told her, then promptly burst into tears. A few hours later Nancy arrived at the door with a bunch of flowers. They were accepted, though not too graciously, I'm afraid.
Though its following was overwhelmingly Catholic, the early civil rights movement in Derry prided itself on its espousal of non-sectarianism. Great respect and affection was lavished on those Protestants who had broken ranks to support our demands - Campbell Austin, Ivan Cooper, above all the hugely popular Claud Wilton, who campaigned unsuccessfully in the Liberal interest under the (unofficial) slogan "Vote for Claud, the Catholic Prod".
The most popular catch phrase in those far-off days - the one that always drew the biggest cheer at rallies - was "British rights for British citizens". In 1968 and 1969 it seemed as if that prospect might be very close.
After thousands of needless deaths over 30 wasted years, the peace settlement now offers much the same terms we were marching for then.