Nobody ever said it was going to be easy. Whoever planted Tuesday's bomb in Markethill, devastating a mainly Protestant village which has already suffered terribly from the violence of the past 25 years, knew exactly what they were doing. The aim was to destroy the peace process. Ironically, they may also have performed an important service in concentrating all our minds on just how difficult these negotiations are going to be and how formidably determined the forces ranged against them.
Given the euphoria which had hung over Sinn Fein's entry into talks and the sense that it was only a matter of time before the unionists also agreed to take their seats at the historic table, this savage reminder of the harsh realities that still exist outside Stormont may be no bad thing.
We have seen similar scenes from places where decent men and women, fundamentally opposed to each other politically, have decided that the time has come to end the bloodshed and to take risks for peace. In Israel, the fundamentalists have all but destroyed any hopes of building trust for the foreseeable future. In Northern Ireland, too, there are people on both sides who believe any settlement which involves compromise is a betrayal of all who have suffered and died. The likelihood is that they will act to prevent it.
At the moment, it seems that the talks have survived this first attack. David Trimble has demonstrated great courage in deciding to bring his party back to the Stormont talks, but it would be foolish for the nationalist parties, particularly Sinn Fein, to interpret this as a sign of weakness.
It was, I think, one of those involved in negotiating a settlement in South Africa who remarked that trust comes only at the end of a long period of talks - it is not there at the beginning. What is needed all the time, he said, is to imagine how the current situation is being experienced by the other side. That is certainly true of the present negotiations at Stormont.
Having reached the table, Sinn Fein should now try to demonstrate some understanding for how this process is perceived by most unionists.
The IRA's recent statement in An Phoblacht is a case in point. To observers able to afford the luxury of relative detachment, this seemed deliberately timed to steady the republican movement's own base in the wake of Sinn Fein's signing up to the Mitchell Principles, but even moderate unionists to whom I spoke last week interpreted it in a much more sinister way. They saw it as the IRA "laying down a marker for the future", that if the negotiations do not go their way they reserve the right to return to violence.
A British official once told me that this is a common phenomenon in the tortuous process which passes for politics in Northern Ireland. Political leaders make comments exclusively directed at their own constituency with no thought for the suspicions their remarks are going to provoke on the other side. When this is pointed out to them, they often seem genuinely taken aback that their words sound so different when heard across the sectarian divide.
Careless talk hinders the development of trust, but violence of the kind which is now threatened by breakaway groups on both sides could derail the whole process and it is essential that nobody is seen to be ambivalent about it.
Both communities want from these talks the promise of a certain and equitable peace. This looms much larger in most people's minds than the political details of a settlement. Nationalists want to be reassured that they will be guaranteed real equality and "parity of esteem". If serious progress is seen to be made on this agenda, pressure will ease on Sinn Fein from its own base and the threat of a return to violence will recede.
On the unionist side, the overwhelming yearning is for peace and it is striking that people seem to accept that sacrifices will be necessary to secure it. Recent opinion polls show a stunning majority in favour of unionist leaders entering the talks process. It is one of the factors which has helped David Trimble to get over the setbacks of the past week, but alongside this willingness to talk goes a deep anxiety about the outcome of negotiations.
Talking to a cross-section of unionists last week, I found the same themes came up again and again. As far as the talks themselves are concerned, they see a confident and coherent nationalist alliance with a strategy for achieving its objective of a united Ireland by consent. By contrast, their own leaders seem divided and fractious.
The British government is seen as indifferent, determinedly neutral on the issue of the Union. They know there are difficult times ahead for David Trimble and fear he will be isolated inside the talks and subject to demoralising sniping from McCartney and Paisley on the outside.
At a deeper level, many unionists believe the political tide is running inexorably against their community. They suspect that British government policy is driven by self-interest, i.e. a determination to prevent a return to violence by the IRA and, in particular, any new bombing campaign on the British main land. "The only test of a settlement will be `Can Gerry live with it? Will he be able to sell it to the IRA'?" one moderate unionist said to me.
Against this background, it would be immensely helpful if Gerry Adams and his colleagues could give the broad unionist community the reassurance it so desperately craves. For a start, Sinn Fein could reconsider its use of language. Yesterday morning, the Belfast News Letter carried a front-page splash showing the devastation caused by the Markethill bomb with the headline: "Gerry Adams `regrets' . . ."
The clear inference was that "regret" was not adequate to assuage the anger in Markethill, where local people believe that local IRA activists must at least have known about the bomb, despite the denials of any involvement. It may even be that the time has come to bite on the dreaded "C" word. Would it really be so difficult for Mr Adams to "condemn" an outrage which Mitchel McLoughlin described as having been committed by "enemies of the peace process"?
In the longer term, there may be other steps which Sinn Fein and the IRA should consider in order to convince the unionist community that the Republican community is seriously committed to the pursuit of peace. Some move on the decommissioning front is the most obvious. We know that the IRA has sworn that not a single bullet will be handed over until a settlement is agreed, but at some stage it may be necessary to make a generous gesture in order to keep David Trimble and his party within the talks, and to make common cause for peace against those who would sabotage the whole process.
Without the unionists, the talks are not worth "a penny candle", another phrase which demonstrates the importance of language to the peace process and which is particularly apposite now.