By Mark Devenport BBC Northern Ireland political editor

Last October, Tony Blair swept into Belfast for a speech at the imposing Harbour Commissioner's office.

The speech provided his prescription for cutting the knot which threatened to throttle the peace process.

The prime minister introduced the phrase "acts of completion" into Northern Ireland's lexicon.

This was code for sweeping gestures by the paramilitaries, especially the IRA, which would restore the trust shattered on all sides by the collapse of the Stormont assembly.

Unionists complained that there should be only one item on any talks agenda, namely paramilitary activity

Just before mentioning acts of completion, the prime minister argued that another "inch by inch" negotiation would not work.

It was time for what Gerry Adams might call the "begrudgery" which bedevilled so many past bargaining sessions to be put aside and for everyone to put their cards on the table.

'Different concerns'

But Northern Ireland being Northern Ireland, Tony Blair had hardly boarded his plane back to London before another "inch by inch" negotiation began.

Republicans wanted to know what acts of completion the government would offer if the IRA made a significant move.

Unionists complained that there should be only one item on any talks agenda, namely paramilitary activity.

But they soon found other parties introducing quite different concerns.

The organisation won't use a term like "disbandment" which even the unionists have backed away from

In recent months, most of the serious discussion has taken place in private meetings away from the formal Stormont talks table.

The term "shadow boxing" is still probably accurate to describe the current state of play.

But at the same time, there is now a feeling that everyone knows what might be in the melting pot - the time has come to bring the mixture to the boil.

'Active service volunteers'

Some kind of statement from the IRA is a necessary ingredient.

The organisation won't use a term like "disbandment" which even the unionists have backed away from.

Another part of any package will be how both an end to IRA activity and the government's side of the bargain can be independently verified

However, could some words be found which could be interpreted as the "standing down" or "end to activity" which the government believes is all important?

At the end of its 1950s border campaign the IRA said all its "full time active service volunteers" had "been withdrawn".

There is no suggestion that the IRA will repeat those words. But the phrase shows that P O'Neill might choose a number of different words to tackle the same theme.

In return for an IRA gesture, republicans will undoubtedly expect the demolition of Army watchtowers in south Armagh.

Other parts of the mix include a significant, and perhaps a visible, act of disarmament, new laws to enable on-the-run paramilitaries to return home and a commitment to the early devolution of policing and justice powers to local politicians.

In that context Sinn Fein could make the big leap and take its places on the Policing Board.

Another part of any package will be how both an end to IRA activity and the government's side of the bargain can be independently verified.

There are a lot of pieces in this jigsaw and a lot of questions yet to be answered.

Chief among these will be the unionist reaction to any deal, which may itself depend on who is in the driving seat on the unionist side before and after the 1 May assembly election.

There's a lot for the prime ministers to ponder. But they may now decide that the time for sitting back and listening to the party's wish lists is over.

If that's their conclusion, the pace of events could accelerate rapidly in the coming weeks.