Most effective diplomatic systems accept the need - at least in principle - for unvarnished comments from their embassies. In practice, however, inhibitions creep into diplomatic reporting because of two sets of concerns.
The first is that something might leak which would be an embarrassment for an embassy's host government and hence for the embassy itself. For example, the Wikileaks cables revealed some extraordinarily frank United States embassy appraisals of host governments. It was this sort of thing that caught out Darroch.
The second and possibly more common concern is that undue frankness from an embassy, even if not made public - but particularly if it were might be disturbing to the home government or at least some members of it. For example, when posted in Jakarta in the late nineties, I sent a report of highly critical comments about Australia over Timor from a leading Indonesian political figure. When that figure became president, I was told that a thorough if not wholly successful hunt for copies of the cable was undertaken.
When serving In India I reported remarks, adding a comment which supported them, by a senior Indian government figure on our detention on possible terrorism charges of an Indian doctor (Mohamed Haneef). I was asked to mute future commentary to accommodate Australian political sensitivities. The doctor was released and won substantial damages for false arrest.
Analogous cases are common enough in diplomatic systems similar to our own.
These inhibitions ironically lead diplomats to do a lot of business on the phone, a form of communication technically easy to penetrate. But the better ones, like Darroch, still try to do their best in writing albeit in highly classified systems because people do need to see their messages. Better information means better policy. Darroch's misfortune was to be betrayed.
The leak is unlikely to be the work of a foreign power as some canvass. If it is, the Brits have real problems. Moreover, while officials can be indiscreet, those at a level to be in receipt of Darroch's messages are not usually driven to break the law by handing over sheafs of sensitive material to a sensationalist newspaper.
While one should withhold unequivocal comment until the results of British investigations are known, it is a reasonable bet that the leak is from a politician. Leaks usually are, and leaks tend towards flood levels at times of intense political or ideological rivalry. This is currently the case in Britain (as well as the United States and, dare I say it, Australia).
Leaks are usually about short-term political advantage, but they can also take events in unforeseen directions.
In betraying Darroch, no doubt some figure or group thought they were doing the right thing by Britain. They should be cautious. In the international relations business they say "never take on the whole room at the same time". Britain has evident issues with Europe. Its aspirations to create new economic linkages with China could be tempered by developments in Hong Kong. It is hard to see any positive developments for Britain's transatlantic relationship arising from these latest events. Darroch's betrayer also betrayed the British national interest.
Given the current disarray in the democratic ethos, it is hard to see any dramatic shift away of the destructive leak as a weapon in Western political armouries. But no nation Britain, the United States or Australia is going to be well served by say-nothing diplomats.
John McCarthy has served as Australian ambassador to Vietnam, Mexico, Thailand, USA, Indonesia, Japan and High Commissioner to India.