Chris West reports from Belfast: "The tension of the marching season is overshadowing the opening of the Assembly"

The first meeting of the new 108-member Northern Ireland Assembly is in every sense an historic event. Since the old Northern Ireland Parliament was prorogued in 1972 there have been several initiatives designed to put power back into the hands of local politicians and in 1974 and 1982 institutions were established but did not last.

The Assembly could move to Stormont, scene of the peace process talks

It is the nature of the new Assembly however, that marks it out as a departure from everything that has gone before. This time it is part of an over-arching series of structures which encompass political relationships throughout the British Isles.

It is legislatively linked to formal cross border institutions involving the Assembly and the Irish Parliament, the Dail, and an East-West Council which draws in Scotland, Wales, the Isle of Man and Westminster.

For the first time in the history of Northern Ireland, at 2.00pm local time on Wednesday all the main party leaders will be together in one room. Ian Paisley, the leader of the Democratic Unionists, will be in the same debating chamber as the Sinn Fein President Gerry Adams.

The Assembly begins life in the Castle Buildings in Belfast

Dr Paisley left the inter-party talks when Sinn Fein were admitted following the calling of the second IRA ceasefire last summer and has sworn not to share power with republicans. The leader of the largest unionist party, David Trimble of the Ulster Unionists, stayed in the talks with Sinn Fein but has yet to speak to Mr Adams.

It will also be a special moment for the SDLP leader John Hume who was one of the key architects of the peace process along with Mr Adams. In the elections his party had the largest share of the vote for the first time ever.

The biggest single threat to the Assembly is posed by the unionists opposed to the Stormont Agreement which set up the new institution. There are 28 of them, not enough to bring it down although they deny that is their gameplan.

David Trimble: becomes First Minister in the Assembly

But they are against the proposed cross border bodies and will try to frustrate attempts to set them up. The reality however, is that unless those bodies are established and running by the end of January next year then the Assembly itself will be prorogued.

The issue of an Executive or cabinet complete with ministers running departments is also contentious. Sinn Fein are entitled to two seats on the executive committee but unionists say they will not share power with them before the IRA begins to dispose of its weapons. This will be a make or break issue.

Lord Alderdice, who was appointed Presiding Officer or Speaker by the Northern Ireland Secretary Mo Mowlam, will start the proceedings by inviting the 108 members of the Assembly to take their seats. Lord Alderdice, who has just resigned as leader of the cross community Alliance Party, will be speaker throughout the period that the new institution is in "shadow" form. Various powers have to be delegated to the Assembly and this is likely to take until next February.

Rev Ian Paisley could block the Assembly's work

At the first meeting the speaker will preside over the election of a First Minister and Deputy First Minister, likely to be David Trimble and John Hume although Mr Hume_s deputy Seamus Mallon has also been mentioned.

Committees will also be set up to look after various "housekeeping" arrangements, including the shape and number of the various government departments which will be devolved to the Assembly, such as health, education and environment. Standing Orders for the Assembly will also be framed.