FEELINGS of insecurity were n ever in short supply in Northern Ireland, on either side of the divide, but they are probably flourishing most these days among the unionist and loyalist community. The latest shootings in Lurgan will accentuate the siege mentality and feeling of being "got at" among the Northern majority.

The underlying causes of their insecurity are three. First, they have a deep distrust of the British government and its intentions for the North. Second, against a background of continuing activity by republican paramilitaries, the nationalist share of the vote has grown, powered by a surge in support for Sinn Fein. Third, the nationalist population has increased and has seized ground that was previously - the preserve of unionists.

Worries about a plot to undermine the Union are ingrained in the psyche of the majority population in the North. Indeed, the Ulster Covenant, inaugurated at Belfast City Hall in September 1912 and signed by 218,000 loyalists, was a pledge to use "all means which may be found necessary to defeat the present conspiracy to set up a Home Rule Parliament in Ireland".

The City Hall itself ceased to be a unionist bastion in last month's local elections, and Belfast now has its first nationalist Lord Mayor, Mr Alban Maginness, and could well get a Sinn Fein mayor in the future. "Use your vote or lose your city" was a unionist slogan. Sinn Fein's counterslogan was "Our City Also". Possession is nine points of the political scene in Northern Ireland.

Population is the fault line of northern politics. The state was established to guarantee a unionist majority and "a Protestant parliament for a Protestant people" in Sir James Craig's famous phrase.

UNIONIST fears have not been allayed by the rise in the Catholic population and the growth of nationalist political power. Traditionally Catholics made up one third of the Northern Ireland population, but now the figure is variously estimated at between 40.6 per cent and 43.9 per cent compared with around 35 per cent in 1971.

Inevitably, this has given rise to unionist concerns that the Protestant population is being "outbred".

This is a matter of much debate among the experts, but the gap has definitely narrowed significantly.

As well as increasing in numbers, the nationalists have been growing in political sophistication. They are "working the system" and coming out to vote in local and Westminster elections at a time when unionists seem to be turning away from politics.

West of the Bann the political map grows greener with every local election. Nationalists emerged from last month's local poll as the masters of Strabane and Cookstown councils (the latter with a Sinn Fein chairman); unionists lost control of Fermanagh, where a socialist councillor currently holds the balance of power but, as one observer put it, "you can see the writing on the wall".

Derry and Omagh have been in nationalist hands for years Limavady and Magherafelt went nationalist in 1993. Unionist sources admitted the "greening" of the district councils was frightening Protestants, causing some of them to "think irrationally" and to feel they were being engulfed by a Catholic tide. "The perception of many Protestants is that there will be a Catholic majority in Northern Ireland," one said.

Unionist sources also said there was a feeling in their community of being trapped in a Catch 22 situation; needing to get their viewpoint across but unable to do so in a way that was not self defeating. "Things like Drumcree have been gifts to Sinn Fein, but Protestants don't know how to express their unhappiness in a way which isn't going to provoke an even higher Sinn Fein vote." The church protests at Harryville have not hurt the Sinn Fein vote, either.

The unionist area of influence is largely confined to the area east of the Bann. But the loss of Belfast, right in their heartland, was a major psychological blow. It reflected the growing electoral muscle of Sinn Fein but also the rise of the Catholic middle class, who have been fanning, out into areas that were previously solidly Protestant.

Even the Malone Road, where once only the servants were Catholic, is now said to be almost evenly balanced between the two sides. The impressive new church of St Ingrid's, with its award winning design, reflects the growth of the Catholic middle class in the area.

AS ONE observer put it: "There is no such thing as a mixed area in Northern Ireland, only areas in transition." Naked sectarianism may be"confined to the ghettos, but analysts say there is an "unconscious bigotry" in the Protestant middle class which makes some of them think of moving as soon as the first Catholic lawyer or accountant buys a house on the road.

As the Catholic middle class grows in strength and confidence, there appears to be a decline in morale among their Protestant counterparts. Analysts say more and more Protestants are choosing English or Scottish colleges for their free third level education and many of them aren't coming back. "Queen's is now largely seen in the Protestant psyche as a Catholic university," said one long time observer.

It could be said that the Catholic middle class was born out of the civil rights movement. Its members have a predisposition to political action that is not shared by their Protestant counterparts. The Protestant business community has tended to shun political activity, leaving the field to "donkeys wearing a sash".

As more and more territory falls to the nationalists, observers are be ginning to speak of the area east of the Bann as "Fortress East Ulster". This loss of ground has exacerbated tensions over the marching season. As one analyst put it, when the unionists see that the land is going "the roads become the only thing they have got left".

This is the significance of the Drumcree church parade set for Sunday, July 6th. It is the unionists" "line in the sand". It has acquired equal significance for nationalists, and that is why Northern Ireland may be facing its greatest crisis since the Troubles began.