When the American experts talked about the need to deny terrorists their safe havens, their British counterparts were embarrassed. The haven for the terrorists they had to deal with was ... the United States.
The point is not that Americans have a double standard when it comes to terrorism. In recent years they have done a great deal to help the British authorities bring IRA terrorists to justice.
It is that terrorism is at once older, more widespread geographically, ideologically more diverse, and far, far harder to eradicate than you would gather from some of the proposals for stamping it out by economic sanctions. or even military action.
For years terrorism has never quite left the headlines. Events such as the Lockerbie bombing, the bomb attacks in the Paris Metro, the sarin gas in the Tokyo underground and the bombing of the New York World Trade Center have kept it there.
Now the issue is moving back to the top of the diplomatic and the political agenda.
There is a widespread fear that the crash of TWA Flight 800 off Long Island was caused by some kind of terrorist. The G7 nations met recently in Paris to try - without much success - to forge an effective counter- terrorism strategy.
President Clinton has just signed legislation sponsored by Senator Al D'Amato of New York, and previously passed unanimously by the House of Representatives, that imposes sanctions on foreign companies which invest in oil in Libya or Iran.
The idea was to warn off European oil companies. But this week Turkey's new government has announced it will build up Iran's oil industry by buying no less than $20bn of oil. Does anyone really imagine that, even if the governments of Iran and Libya were to be vaporised tomorrow, the problem of terrorism would disappear?
What about Syria, for one thing? Damascus, too, has supported terrorism in the past. Yet Washington does not include Syria in its anathema, because the State Department hopes to involve the Syrian government in the peace process with Israel.
Now the New York Times has reported that much Middle Eastern terrorism was financed not by governments but by private individuals. According to the head of the State Department's official counter-terrorism office, one wealthy Arab individual is suspected of helping to finance a wide range of terrorist activities by Islamic extremists, including the murder of Western tourists in Greece; bombings by Algerian Islamists in Paris; and other terrorist activities.
The fundamental strategy behind terrorism is to enable weak groups to embarrass and ultimately defeat powerful empires by "externalising" their latent violence. The ruling state must be made to respond to terrorism in such a way that its power is exposed as resting, ultimately, on force. The philosophy and the techniques have been widely borrowed - in India, South America, Germany and Italy, by Basques and Kurds and many other groups. The state of Israel was founded by people, some of whom not only practised terrorism, but also defended it with powerful political and moral arguments. Terrorism, in fact, is a deeply ingrained part of the world's political system. The question is what to do about it.
There is a plausible argument that terrorists should be treated simply as common criminals; to treat them as special (because of their political motives) is perversely to legitimise them. This may be true, but special means are needed to arrest and try them. Precisely because terrorists often have the resources of governments behind them, they are hard to catch. And because they commit their crimes on behalf of a cause, the danger is that for every terrorist you catch, a hundred more will take his place.
This, certainly, is where international co-operation can help, and indeed a great deal of international co-operation already takes place. That is why it is important that governments should act, as Canada's foreign minister Lloyd Axworthy said pointedly last week, "in concert, in co- operation and co-ordination - not unilaterally".
That is why it would be bad if the United States government insisted on riding roughshod over European governments if they didn't agree. Equally, it would be foolish of European governments to underestimate the surge of indignation that is rising in the US against those foreigners who do not, in their opinion, take terrorism seriously.
The best way to ban terrorism, of course, is to remove its causes. It is born of a burning resentment of injustice or a commanding vision of a better future. But, as we have seen in Israel and in Ireland, to remove its causes proves virtually impossible.
Murder has always been with us. Our societies fight it, on the whole successfully, and we punish it severely, but we know we are not likely to abolish it. If we were wise, we might acknowledge that we may never abolish terrorism, but that we can fight it more effectively. At least then we should not tear the international system apart under the illusion that we can stamp out anger, hatred and a sense of loss.