Three other councils - Fermanagh, Cookstown and Strabane - also lost their Unionist majorities. The results amounted to the clearest indication yet of the impact on the political system of fast-changing religious demographics.
Other explanations offered for the general nationalist advance included a new Catholic confidence in politics, apathy among the Unionist electorate and alleged electoral abuse by Sinn Fein.
The votes for the two main parties - the nationalist Social Democratic and Labour Party, and the Ulster Unionist Party - either remained static or dipped a little. But Sinn Fein, bettered its Westminster performance to take almost 17 per cent of the vote, and the smaller loyalist fringe parties also did well.
The Sinn Fein performance means that an increasing number of nationalist voters are ignoring the appeals of Mr Hume and nationalist leaders in the Irish Republic not to support republican candidates in the absence of an IRA ceasefire.
The question of whether the Sinn Fein vote was boosted illegally was raised by John Hume, the SDLP leader, who said yesterday: "The only vote that has risen is Sinn Fein's vote. There are two reasons for that: one is the Drumcree factor ... and of course there are also very serious questions to be investigated about the abuse of the electoral system."
However Pat Bradley, Northern Ireland's Chief Electoral Officer, described this allegation as "really totally at odds with reality." He said the party would need to convince the Government of the need to change the legislation.
Belfast has already experienced a phenomenon similar to the pattern of "white flight" in some American cities, with Protestants moving out to satellite towns as the Catholic population steadily increases. This may be accentuated by the new situation in City Hall, where the Unionist domination of more than a century has been ended.
Control of the city will rest on the outcome of the wheeling and dealing which can now be expected to take place before the election of Lord Mayor in a few weeks time. Much of the hard bargaining will centre on the moderate Alliance party, whose six councillors appear to hold the balance of power.Reuse content