Seventy two days earlier in Berlin, the last time the fifteen men had gathered together, the news was equally dramatic: it was 24 March and the skies over Serbia were darkening with the shadows of Nato's bombing squadrons.
Yesterday as he broke away from the group gathered on the steps outside Cologne's Gurzenich building, the Prime Minister was intercepted by his ever-present spokesman, Alastair Campbell, to hear the news. He remained impassive.
Nobody in Cologne wanted to speak too soon or display triumphalism but inside the summit the confident mood quickly took hold. As Gunther Verheugen, Germany's Europe minister, swept through the large, modern Maritim Hotel, close to Cologne's historic cathedral, there was no hiding German relief at the events unfolding in Belgrade.
He was, the minister told the world's media, proud of the way that the German government had balanced diplomacy with the military campaign. "We have reached a moment where it is fair to say we are at a turning point," he added.
The diplomatic track had finally won they day, albeit with the help of Nato's overwhelming military superiority. But if diplomacy has indeed won out it has been a tortuous road.
The twin track strategy of bombing and talking kept the Russians engaged and a maintained a vital channel of communication to Slobodan Milosevic. As the bombing dragged on, maintaining unity within the nineteen Nato allies was also a struggle.
Many of the most difficult trade-offs were not with Belgrade - but between the US and its Nato allies over bombing targets and ground troops, or between Washington and Moscow over the peace plan.
The diplomatic track began in the ruins of the Rambouillet peace agreement, the deal which was supposed to be the basis for a lasting settlement in Kosovo. Ministers and negotiators laboured at the elegant chateau in the French countryside to put together a text, but the process had an air of failure about it from the outset.
On March 19, the talks collapsed. The result was Nato's decision to head for war, the first in its 50-year history. Nato believed that Mr Milosevic would fold as its aircraft delivered pinprick strikes to show that its threats were in deadly earnest: this backfired badly.
Within a week, it was clear that something else would have to substitute for Rambouillet, but it took much longer for any effective process to emerge.
Nato's only response to Serb outrages against Kosovar civilians was to drop more bombs in an increasingly desperate effort to break Belgrade's resolve. But the bombs also hit hospitals and civilian convoys, causing international outrage. Pressure grew on the coalition government in Bonn - against the backdrop of huge anti-war demonstrations - and the need for an end to the bombing grew ever more pressing.
No Western politician has had a more uncomfortable war than Joschka Fischer, the Green and one-time peacenik who is now Germany's foreign minister and a central player in the SDP/Green coalition. Under pressure to broker an end to the bombing, Mr Fischer's department of foreign affairs, embarked on a concerted push for peace. Germany was ideally placed to make it.
A member of Nato, Germany holds the presidency both of the EU and of the other group which has emerged as a forum for diplomacy, the G8 group of seven wealthy nations plus Russia.
From these facts emerged a strategy: Germany would try to align the positions of all the big players with a path acceptable to Nato, thereby isolating President Milosevic and robbing him of his only ally, Moscow.
To this end Kofi Annan, United Nations Secretary-General, was invited to a special meeting of Europe's heads of government in Brussels in April. By now German officials had drafted ideas for a possible route to peace, including a pause in the bombing.
But the reaction illustrated the difficulties ahead. With early warning from Mr Blair's entourage that the idea was doomed, Gerhard Schroeder, the German Chancellor, avoided mention of the specific proposals but won backing for a broader diplomatic strategy.
The strategy that emerged relied on a few key foundations. First, the West would not get into a direct negotiating session with Belgrade, so any talks had to go through other channels. Russia had to be kept on side: not just so that a UN veto could be avoided but so that Mr Milosevic realised that he was diplomatically isolated. And the United Nations was to be kept at a distance as long as possible, until it became essential to involve it in drafting a final agreement.
What resulted was a constant shuttle between Washington, Bonn and Moscow for the US Deputy-Secretary of State, Strobe Talbott, an old Russia hand who had been a journalist for Time magazine for most of his career. Mr Talbott had the trust of the President - Mr Clinton used to make him eggs on toast and cups of tea when the two shared a house in Oxford. And he knew Moscow intimately.
Working with Viktor Chernomyrdin, the Russian negotiator, Mr Talbott tried to win over Russia to America's strategy. Although never totally in bed with the Serbs, the mood among the Russian leadership had been ominous as the air campaign got underway.
Adamant that Russia had to be taken seriously, Boris Yeltsin had warned that Nato was in danger of drawing Russia into a Third World War. But three weeks into the bombing, in a key turning point, he decided to appoint a special envoy to negotiate peace in the Balkans.
His choice of the pragmatic Viktor Chernomyrdin marked a distinct softening in Moscow's position. The former Prime Minister and gas baron had strong ties to the West, and was less strident in his opposition to Nato than the man whom he supplanted from the task of acting as Russia's intermediary, Yevgeny Primakov.
Only three weeks earlier, on the eve of the war, Mr Primakov had demonstrated Russia's anger with Nato. In a theatrical gesture worthy of the Cold War he turned around his aircraft in mid-air when en route to Washington for talks over international loans. Five days later, he went to Belgrade for a trip that only served to underline Russia's pro-Serb sympathies, rousing fears that these could prompt Moscow to give concrete support to Belgrade, including arms.
Mr Primakov was accompanied on the trip by Russia's hawkish Defence minister, Marshal Igor Sergeyev, and military and foreign intelligence chiefs. The West winced as pictures beamed around the world showing the Russian premier laughing and joking with Mr Milosevic.
Unlike Mr Primakov, the new envoy's relationship with Slobodan Milosevic was cool. At home his mediator's role was angering Communist and nationalist opponents in parliament and - more importantly - the Russian military establishment, which remained vigorously opposed to making concessions to Nato. There were rumblings, too, from within the foreign affairs establishment; the Foreign Minister, Igor Ivanov - another key player - was generally perceived to be less conciliatory than Mr Chernomyrdin.
Matters were further complicated by domestic political upheaval, triggered by Mr Yeltsin's decision to throw out Mr Primakov and appoint a new premier, Sergei Stepashin. A failed attempt by the State Duma to impeach the president was a blow for the anti-Yeltsin Serbs but also deepened the sense of instability.
Not until the 6 May meeting of G8 foreign ministers in Bonn did Russia signed up to the principles of a deal. Wide gaps remained on the timing and nature of a Serbian pullout, but it was the basis for a deal.