By Mark Devenport BBC Northern Ireland political editor

First we had the brawl in the hall. Now we have the stir on the stairs.

The image of Northern Ireland's health minister, Bairbre De Brun, challenging police officers as they made their way down the Stormont stairs after searching her party's office inside Parliament Buildings was every bit as extraordinary as last year's near fisticuffs in the Great Hall.

However, the two scenes symbolise very different moments in the history of this process.

The brawl signified hardline unionist anger after the Good Friday Agreement - in the shape of David Trimble and Mark Durkan - survived against all the assembly odds.

By contrast the stir appears to represent if not the end of the Agreement then certainly the end of this phase of the peace process.

Bairbre de Brun: Sinn Fein minister claimed police raid on Stormont was a plot to undermine the party

The situation, as Mr Trimble himself put it, is fluid. Whilst the government may argue that any sanctions should await the outcome of the police investigation into IRA intelligence gathering within the Northern Ireland Office, the political clock is ticking a lot more quickly than the legal timepiece.

All the pouring over calendars which we observers engaged in after the Ulster Unionists set their January deadline for withdrawal from government is now rendered academic.

Events on the ground are once again dictating the pace of politics.

It is impossible to draw definitive conclusions about the police search of Sinn Fein's offices and the investigation into intelligence gathering while, at the time of writing, people are still being questioned.

Lateral thinking

Almost all the unionist complaints about republican behaviour - Castlereagh, Colombia and now the third "C" of Castle Buildings - are allegations rather than proven events.

History may show Sinn Fein to have been the innocent victims, as they claim, of a 'securocrat conspiracy'.

But politicians are not historians. They will make their decisions in the coming days and weeks without the benefit of hindsight, but with the hope of a bit of foresight about what the voters might do if and when we have fresh assembly elections.

With that in mind we may be on the verge of either another suspension of devolution or the dissolution of Stormont to prepare for early elections.

The chances of Tony Blair or Bertie Ahern pulling any rabbits out of their hats next week appear even slimmer than before.

David Trimble: Warned the British Government to act against alleged republican activity

It is hard to see them abandoning the institutions set up under the Agreement. But they may have to indulge in some lateral thinking about how to preserve them in aspic until the local politicians are ready to resume full-blooded participation.

Without prejudging the police inquiry, there may be an irony in this latest episode for Sinn Fein.

Almost all politicians readily grasp leaked documents if they are put their way.

Remember the leaks Mo Mowlam grappled with in the run up to the referendum on the Agreement, which apparently served hardline unionist interests?

But Sinn Fein isn't like other parties because of its historic umbilical links with the IRA.

So if the movement has received official documents, the purpose they might be put to may be considered a moot point.

For Sinn Fein, a bit of constructive ambiguity has paid dividends in the past, when the party has taken credit for persuading the IRA to abandon violence, but avoided blame for IRA attacks.

If, as Jeffrey Donaldson claims, this is the final nail in the Agreement's coffin, Sinn Fein may consider blaming not only the securocrats but also their failure to resolve their own ambiguous identity.