In the field of diplomacy, as distinct from that of military operations, leaks, indiscretions and premature publication of opinions which were presumed to be private are often no more than embarrassing, sometimes even hilarious. But the reason that all foreign ministries employ costly and sophisticated encryption techniques is that they can sometimes be positively damaging. It is likely that the current batch of WikiLeaks will include all these categories.

The leaking of the valedictory dispatches of some former British heads of diplomatic missions has often been more embarrassing to their authors than to the targets of their fulminations. But the fact that former foreign secretary Margaret Beckett put a peremptory end to the practice suggested that the embarrassment sometimes stretched to the government of the day.

In any event, astute use of the Freedom of Information Act has ensured that many more such despatches, as well as other supposedly private opinions and sources of advice, have recently been published, well before the application of the 30-year rule which requires that most official documents must be freely released.

Britain and many other governments subject to similar legislation have had to live with such a situation, although with increasing difficulty when the issues concerned touch on national security.

Does it really matter whether a former British foreign secretary should air their view that the Prime Minister of Italy was unfit to govern? Or that the British press over the past weekend should be full of stories of alleged murky dealings by the President of France? Not really, because the relationships between the countries concerned encompass much wider issues than the personalities involved.

Real damage can, however, be caused when personal trust, honour or national security are involved. When yet another former foreign secretary was reported in the aftermath of 9/11 to have described a head of government with whom he had been negotiating as being incapable of opening his mouth without lying, he was frozen out, at a time when Britain had important interests to pursue.

What will be damaging in the Wikileaks, then, will be revelations about views on the part of senior political figures about individuals or nations who may be able to retaliate, or when the cultivation of personal trust is essential in progressing whatever interests may be in play. This will apply particularly in relation to states which have an elevated sense of national honour and, more generally, to the Muslim world. Afghanistan, Iran and Pakistan spring immediately to mind.

The proliferation of the right of freedom of information has already caused ambassadors to damp down the fires in their bellies, at the cost of the value which they can add to their political masters. The increasing practice of wholesale leakages may extinguish them altogether. Or perhaps, sadly, diplomacy will revert to the Talleyrand-like practice of dissimulation and secret personal emissaries.

Former British diplomat Sir Hilary Synnott is consulting senior fellow at the International Institute for Strategic Studies