It has logged MPs' questions, letters to ministers from members of the public, and newspaper leading articles. Until a few days ago, civil servants report, their 'indicators' produced nothing to suggest that Western governments should rethink their unheroic but pragmatic policy of keeping out of the fighting.
There was, they found, concern after each atrocity - sometimes intense concern, as after the pictures of detention camps last year - but never 'cumulative concern', building up into the kind of public outrage that forced the West to create 'safe havens' for the Kurds of northern Iraq in 1991. Indeed, the highest level of anger officials noted was when Lance-Corporal Wayne Edwards was killed delivering humanitarian aid in Bosnia in January: anger not against his killers but against the Government for putting troops at risk.
Last week, all that changed dramatically. Pictures of desperate refugees clamouring to leave Srebrenica, of children blinded and maimed, had already stirred public opinion. (A Daily Telegraph Gallup poll, carried out before Easter, showed that 61 per cent wanted international intervention.) Then came an onslaught from what is still the most explosive force in British politics.
Eyes ablaze, chin aloft, Baroness Thatcher, appearing on the BBC's Tuesday evening news programmes, deployed her unrivalled talents for portraying complex issues in black and white. 'We cannot let this go on,' she proclaimed. 'We have become a little like an accomplice to massacre.' She was ashamed of the EC's inaction, of Europe's lack of conscience. Douglas Hurd, the Foreign Secretary, had used a 'terrible and disgraceful phrase' when he had said that to arm the Bosnian Muslims would be to create a 'level killing field'. She was 'thankful' that 'in the Battle of Britain . . . the prime minister was a lionheart'. At that time, Britain had proper equipment; now, an arms embargo was denying it to the Bosnian Muslims.
The Government's first reaction was to dismiss Lady Thatcher's comments as, in the words of Malcolm Rifkind, the Secretary of State for Defence, 'emotional nonsense'. There would be no change in policy: no air strikes on Serbian positions or supply lines, no lifting of the arms embargo. Even among the backbench Thatcherites, the reaction to her intervention was muted.
By yesterday, however, as Srebrenica looked ready to accept the inevitable, the tone had changed. Tribune, the left-wing weekly, had proclaimed: 'Margaret Thatcher is right.' John Smith, the Labour leader, said an ultimatum should be issued to the Serbs, backed by the threat of air strikes. Lord Owen, the EC peace envoy, said the Serb supply lines should be bombed. Mr Hurd promised stricter enforcement of sanctions and emphasised the bombing option had not been ruled out. Across the Atlantic, too, the mood shifted. President Clinton declared all US military options, except sending American ground troops, were open.
Not all - or even most - of this can be put down to Lady Thatcher's merciless denunciations. The imminent fall of Srebrenica was bringing home to European and US leaders that their peace efforts had failed to halt Serbian aggression. And Lord Owen and others continued to reject her call to arm the Muslims. But, once more, Lady Thatcher had succeeded in galvanising opinion. If nothing else, her successors in government were forced to explain themselves.
AMONG the many ironies in the resurrection of Lady Thatcher's influence on British politics is that she said nothing new.
In August 1992, she called in the New York Times for Serbia to be threatened with military strikes. 'The West was passing by on the other side,' she said. Serbia was being encouraged 'by Western inaction'.
In December, writing in the European newspaper, she used almost exactly the same language she used last week. The West was 'more like accomplices' to genocide, she said. There should be air strikes on Serbian positions and the Muslims should receive arms to defend themselves.
Her view has been consistent and peculiar. While most commentators see the Balkan civil war as the result of nationalist tensions loosed by the fall of communism, Lady Thatcher sees it as a result of aggression orchestrated by the unreformed communist Serb leadership in Belgrade. Her gut feeling, says one former Balkan diplomat, is that 'the Communists - or National Socialist Communists in Serbia - had been allowed to grab all the arms and suppress people proposing democracy'.
Lady Thatcher, who still sees foreign ministers during her many overseas visits, has an extensive network of contacts in the Balkans as in other parts of the globe. On occasions - at least according to her friends - she has influenced events behind the scenes. Eighteen months ago, for example, a Slovenian leader appealed to her to help as a tank column made its way from Belgrade to Slovenia. Her assistance in phoning the Foreign Office, Downing Street and the Bush administration, achieved a temporary halt to the advance. Why should overseas politicians appeal to an ex-prime minister rather than an incumbent? 'When you're in trouble,' said one Thatcher ally, 'you call the fire brigade, not the WI.'
Her previous pronouncements, however, were briefly noticed, then forgotten. The difference last week was the style and timing of her intervention, not the content.
Last week, her office phoned the BBC and said that the former prime minister was furious about the failure of Western policy, and the media blitz began. After her overture on the BBC's Six O'Clock News, she went on to be interviewed by ITN, BBC Newsnight, the BBC World Service and three US television networks.
To seasoned Thatcher-watchers, the ex-premier's television performance was a reminder of what she used to be like in private. 'I wondered,' said another Tory loyalist, 'why she had come out so strongly. One thought was that she was not tapping into the nation's concerns so much as articulating an anti-EC, anti-John
Major, anti-Government feeling. When I heard her say, 'I am angry,' I thought, 'She was always angry, that was the trouble.' '
John Major's Cabinet has always tried, in public at least, not to rise to the bait of a woman they now regard as detached from government. Last week, however, Mr Rifkind and Baroness Chalker, in the House of Lords, felt confident enough to use strong language and meet fire with fire.
If anything, the effect of her comments on Labour was more marked than the effect on the Tories. With many Labour MPs representing large numbers of Muslim constituents, the slaughter at Srebrenica had particular poignancy. Yet, on Wednesday, David Clark, the defence spokesman, had verged on the bipartisan in his Commons response to Mr Rifkind. To many Labour MPs, it looked as if Lady Thatcher was being allowed to emerge as leader of the Opposition.
Probably more important, they noted public opinion in the Gallup poll, published on Thursday. Fourteen MPs, from left and right of the party, published a statement calling for the commitment of troops. After talking with Mr Clark and John Cunningham, the shadow Foreign Secretary, Mr Smith agreed on Friday to toughen the Labour line.
The imminent fall of Srebrenica was the catalyst. But the position of Lord Owen was also influential. His advocacy on Friday of the use of air power is not new; it pre-dates his appointment. With the Muslims and Croats signed up to his peace plan, Lord Owen viewed military force as legitimate pressure on the Serbs to come to the negotiating table. In an article in Foreign Affairs in February, Lord Owen said the West could increase sanctions, 'then tilt the balance of force by the use of air power to pressure the . . . Bosnian Serbs to sign up'. He added: 'Tipping the balance to force a recalcitrant party to accept a just and equitable package is, in my view, wholly legitimate diplomacy.'
SOME commentators, however, speculated that Lady Thatcher was not really addressing British politicians at all. Her remarks, they suggested, were directed across the Atlantic, in an attempt to repeat the resolve-stiffening that she achieved with President Bush - according to her personal publicity - after the Iraqi invasion of Kuwait.
Lady Thatcher, however, like every other British politician, has almost no influence on the present US administration. Her attack on Western policy was widely reported, because it came at a moment of crisis in the war when none of America's leaders was saying anything about Yugoslavia early last week.
By Friday, Mr Clinton had been forced to become more aggressive. He strongly condemned the Serbs and said he would consider punitive action.
He knows that US politicians and voters are overwhelmingly against sending ground troops to Bosnia, but would probably support limited air strikes. The President shares the lack of enthusiasm for military action. During the election campaign he berated President Bush for failing to stop the Serbian aggression, but once he reached the White House he U-turned on Yugoslavia, as on many other issues, and became, if anything, more cautious than his predecessor.
He is particularly concerned about public sympathies for the Serbs in Russia: if America backs the Muslims, he calculates, it will create pressures on Boris Yeltsin to do something for the other side and thus further destabilise him.
The strongest sign of the mood of extreme caution in the Clinton White House was its reaction to a report from an expert team that visited Bosnia in February. Led by Hugh Hamilton, deputy adviser for East European assistance at the State Department, it insisted that there was only limited point in supplying humanitarian aid. More Bosnians were being killed as a result of the fighting, it found, than were dying of starvation.
The team proposed 'safe havens' for the Muslims, protected by an international military force. The experts were told they had been sent to look at relief, not to recommend military intervention. The White House tried, but failed, to suppress its report.
But the inexorable and brutal advance of the Serbs may have made a policy of keeping out unsustainable. In the early hours of yesterday the UN, with US support, adopted Mr Hamilton's proposals and demanded safe areas for Bosnian Muslims, a call to action that is almost certainly too little and too late for the inhabitants of Srebrenica.
Whether it will do anything for the inhabitants of other Bosnian towns remains to be seen. Politicians out of office can easily talk of ultimatums, action and the dictates of conscience. Those who may actually have to commit troops or order bombing raids remain cautious. Mr Hurd argues that any course of action has to be measured against its likely gains. He remains unconvinced about the effectiveness of air strikes and, with the Serbian economy in disarray, he still sees tighter economic sanctions as the best way forward.
In London, as in Paris and Washington, the rhetoric may have changed, but it is far from clear that there has been any real shift in policy.