Northern Ireland's new politics came into undignified collision with the old yesterday as David Trimble's re-election as First Minister was followed by ugly scenes outside the Stormont chamber. Nationalist and Paisleyite Assembly members pushed and shoved after loyalist barracking of the Ulster Unionist leader degenerated into the physical.

Political knockabout moved from the metaphorical to the actual after the third and finally successful attempt to restore Mr Trimble to the office of First Minister, with Mark Durkan of the SDLP as his deputy.

Mr Trimble's resumption of the office he vacated in July, to push the IRA into decommissioning, was hailed in several quarters as the final breakthrough that would make possible a new period of stability in the peace process.

But the fracas cast a shadow over the optimism of the moment, serving notice as it did that the Rev Ian Paisley's Democratic Unionist Party and others would continue to try to destroy the peace process.

Denouncing the DUP and what he described as "a near-riot situation", Mr Trimble declared: "Now we know the hypocrisy that lies under those sort of matters. We have to provide people with a degree of calm and attention to business."

His sentiments were echoed by the Irish Taoiseach, Bertie Ahern, who said: "Those who are determined to pursue the failed politics of the past will not succeed ... Stable and inclusive government is essential."

The Trimble-Durkan ticket received a majority of Unionist and nationalist members of the Assembly after the centre-ground Alliance party redesignated three of its members as Unionists for the day.

This came after Mr Trimble's defeat last Friday when he was 0.8 per cent short of the required Unionist majority. Yesterday, he received 70 per cent of the vote overall and 51 per cent of the Unionist total.

Rejecting Mr Paisley's calls for elections, the Secretary of State for Northern Ireland, John Reid, said there was no need to have a fresh contest before the scheduled date of May 2003. Hailing the vote as a "massive" step forward, he added: "For the first time we can move forward, confident and with a real expectation of stability."

The DUP had held up the vote with delaying tactics, peppering the Assembly's Speaker, Lord Alderdice, with a sustained series of points of order. Mr Paisley denounced the Alliance redesignation as "cheating and rigging and deceiving". After the vote, when Mr Trimble and Mr Durkan addressed the media, his son, Ian Jr, and others heckled loudly.

One called out to Mr Trimble: "You're a traitor David and you know it", and after some moments the scuffles broke out.

The two heads of Northern Ireland's government then took office. Some observers described it as historic, while others noted that the political scene still contained traces of the prehistoric.