If a diplomat is "an honest man sent abroad to lie for the good of his country" (Henry Wotton, 1612), then oil industry execs used to be the business world's equivalent of diplomats.
The big international companies were chronically optimistic about the extent of their reserves, and state-controlled oil companies were even more prone to exaggeration. Now we have the spectacle of oil companies telling the truth about oil supplies - or at least more of the truth than usual.
The occasion was the Oil & Money conference in London on October 30 and 31, and the most spectacular truth-teller was Christophe de Margerie, CEO of the French oil firm Total, one of the international "big five."
Last year his predecessor, Thierry Desmarest, caused a flutter in the industry by predicting that world oil output would peak around 2020.
De Margerie's warning was more dire. He said that "100 million barrels (per day)... is now in my view an optimistic case."
He was referring to the International Energy Agency's estimate that world oil output would reach 116 million barrels per day by 2030, and the slightly more optimistic U.S. government prediction that it will reach 118 million.
Even these estimates are really a forecast of crisis, since calculations based on current trends (like 15 per cent annual growth in Chinese demand) suggest that 140 million barrels per day will be needed by 2030.
The implication of de Margerie's remarks is that the crisis is coming a lot sooner than that.
World oil output is nearing 90 million barrels now, but it's never going to reach 100 million barrels per day.
Peak oil may be just a few years away, or it may be here right now.
The concept was first broached by American petroleum geologist M. King Hubbert, who noticed that the curves for oil discoveries and oil production were a very close match.
At that point, in 1956, Hubbert was the director of research for Shell Oil, and the focus of his research was American oil production, then still the biggest in the world.
Hubbert noticed at that time that the shape of the output curve closely fitted the curve plotting the growth of American oil reserves during the years of the great discoveries in Texas, Oklahoma and California.
Hubbert simply assumed that the production curve would continue to match the discovery curve and predicted that U.S. oil production would peak and start to decline in 1970.
That is exactly what it did, and American oil production is now down to about half of the output in that peak year. Hubbert's own forecast was that peak oil production worldwide would arrive in the 1990s.
The discovery of two giant new oil fields in the 1970s (probably the last two) in the North Sea and the Alaska North Slope pushed that date forward a bit.
One of Hubbert's successors as chief of research at Shell, Colin J. Campbell, subsequently calculated that peak production globally would not arrive until 2007. In other words, now.
It is still deeply unpopular in the oil industry to talk about peak oil, but essentially what de Margerie was saying, albeit in a cautious and coded way, is that it is here or nearly here.
The same sort of talk is coming from Rex Tillerson, chairman of ExxonMobil, who told the Financial Times earlier this year that he believes oil production from sources outside the Organization of Petroleum Exporting Countries would soon level off.
And OPEC is generally assumed to be pumping very close to maximum capacity.
The International Energy Agency predicts that demand for oil will rise by 2 per cent annually until 2012, which means that total demand by then will reach around 100 million barrels per day.
De Margerie, Tillerson and other insiders are suggesting that supply will not, which will have a profound impact on the price not just of oil but of practically everything else.
The recent surge in the price of oil, which may see it reach $100 a barrel in the near future, is largely a mirage caused by the collapse in the value of the U.S. dollar. (The price of oil is generally quoted in U.S. dollars, but the cost of a barrel of oil in Euros or yen has risen far less dramatically this year.)
But the longer-term trend, which saw the price rise fivefold between 1999 and 2005, was driven by the tightening supply situation as demand raced ahead of production.
It will get a lot worse if de Margerie is right, and he almost certainly is.
Gwynne Dyer is a London-based independent journalist whose articles are published in 45 firstname.lastname@example.org