Like Queen Mary, who had Calais engraved on her heart, Mr Blair will have Belfast and Belgrade stamped on his. He must continue to hold public support for the peace in Northern Ireland when the auguries are grim. At the same time, he must stiffen support for bombing Serbia when the gains are looking unsure and public nerves are starting to jangle. Mongering peace and war at the same time is a draining combination.
The Northern Ireland peace process was always going to be an exercise in long-distance running. As the anniversary approaches, it is looking like a marathon with random hurdles and ditches inserted to test the spirit of the weary participants. At such times the Prime Minister's job is a lonely one. and especially so for Mr Blair. Northern Ireland and foreign policy have not, in the past few years, been the focus of Labour interest.
Grown unused to office, the party was content to wrap itself in the general pieties of pro-republicanism and some highly selective likes and dislikes about abroad: Pinochet bad, Mandela good, Northern Ireland civil rights activists good, Unionists bad.
Anyone who thought much further than that was deemed dangerously complex and not quite on message. The remnants of this intellectual laziness persist on the far left of the party today, where Michael Foot is an unbalanced apologist for Croatia, while Tony Benn considers the war against Serbia to be a US imperialist plot against a proud Slav nation.
Few of Mr Blair's cabinet colleagues have the experience or interest in Nato matters or Northern Ireland to be much use to him right now. Robin Cook has his hands full with a media war fighting an extraordinary degree of anti-Nato bias in the BBC's reporting.
George Robertson is a dab hand at being pro-Nato, but he is overplaying it badly with references to Serb "genocide". Genocide is the attempted killing of an entire race. If Mr Robertson cannot convince us of the need for air strikes without inflating the Serbs' record of repression in Kosovo into a second Holocaust, we really are in trouble.
On the peace front, Mo Mowlam has fronted the peace process with aplomb, but suspicion has deepened among moderate Unionists that she errs too much towards letting Sinn Fein get away with not decommissioning arms.
For his part, Mr Straw stuck his nose in at exactly the wrong time by calling for judicial review of the release of four IRA prisoners who had been convicted in the English courts but failing to get their release stopped - his first tactical blunder since taking office. Fortunately, Mr Blair was provident enough to squirrel away a senior member of staff for just such a testing time in the shape of Jonathan Powell, a former senior diplomat who is the link to Charles Guthrie, the Chief of the Defence Staff, and who also attends to the nuts and bolts of the Northern Ireland peace process. Quite how Mr Powell organises his week at the moment is beyond comprehension.
It is tempting to say that there is a screaming contradiction between our tolerance of punishment beatings, our tolerance of low-intensity violence, the selective interpretation of agreements in Northern Ireland - and our readiness to go into conflict with another power that behaves in similar ways.
Indeed, a number of voices sceptical of the peace process, of involvement in Kosovo, or of both, have started to point this out. It is easy to summon up the outrage: what are we doing bombing Slobodan Milosevic's military installations while we are striving to keep terrorists at the negotiating table in Ireland?
But it is different. Obviously so, because Ulster is a province of the United Kingdom and thus unavoidably London's problem, whereas we clearly had a choice about whether we intervene in the Balkans. Having embarked on the peace process - a measure which was popular with mainstream political opinion everywhere and which brought him his first international laurels as leader - Mr Blair is anxious to maintain any momentum he can muster, however ominously the sludge of resistance and resentment thickens in both the Republican and the Unionists camps.
On Monday, the Irish leader Bertie Ahern and Mr Blair flew to Northern Ireland in an attempt to reach an agreement on arms.
The Prime Minister can hardly be encouraged by Gerry Adams' words in an Observer interview the day before: "Anyone who thinks I'm hardballing, negotiating, going down to the wire, is failing to understand that this Sinn Fein leadership cannot deliver decommissioning."
Releasing the location of a few buried bodies, the IRA's grisly idea of a positive gesture towards advancing the process is no compensation for some modest, verifiable display of weapons forfeit. Bodies are about the IRA's past behaviour; decommissioning is about its future.
One day, the paramilitaries may accept that the forfeit of arms is not to be equated with weakness. But that day is likely to be further away than Mr Blair believed this time last year.
The peace process consists of multiple bridges of ambiguity over which the various parties have so far tip-toed in order to keep the whole edifice from crumbling. The outstanding one is that Sinn Fein never signed the Good Friday agreement, and thus cannot be bound by it. As Mr Adams pointed out, the parties are pledged only to use their "good offices and influence" to achieve decommissioning, and so cannot be censured if they do not actually deliver it.
If, on the other hand, the Government presses ahead with the creation of an all-party executive without any sign of a weapons handover, the Unionist leader David Trimble is in grave danger of suffering the same fate as his predecessor Brian Faulkner, toppled by his own party in 1974 because it was pushed too far by London to accept the Sunningdale agreement on power-sharing. To destabilise moderate Unionism. now would be a grave miscalculation.
The only ambiguity left to indulge is the wearisome one of extending the timetable for the creation of cross-border institutions and postpone the final accord. It is not war but it is far from a stable peace either.
Mr Blair faces two of the key challenges to peace in our time. If he fails in the Balkans, he will be accused of lacking caution. If Mr Blair fails in Ireland, he will be blamed - by each side - for not having been being brave enough. It is enough to make you wish him luck.Reuse content