On Tuesday morning at 10.30, an hour after the release of the official inflation figures, what is becoming a familiar ritual will unfold. Mervyn King will write to Alistair Darling explaining why inflation is so much above the official target.

He may say, as at the Commons Treasury committee last week: “Provided we do not impede the required adjustment, we will come through this temporary period and resume a path of normal economic growth with inflation close to target.”

The chancellor will respond, saying he understands the Bank of England governor’s difficulty, but has faith in his ability to get inflation back down.

These letters, available for all to read, are not in the Robert and Elizabeth Barrett Browning class but are an important part of the policy process. Tuesday’s will be only the third in more than 11 years of Bank independence, and all three will have come in the latest 18 months.

The rules require a letter each time consumer price inflation rises above 3%, followed by another three months later if it stays there and so on. King’s first letter, last year, said inflation would come down quickly and it did. He wrote in April and by July inflation was below the 2% target, though this was only a temporary respite.

His second, this June, predicted inflation would rise further, to “above 4%” in the second half, before it dropped back below 3%. He laid the blame on soaring energy and food prices.

What will he say this week? Inflation is rather higher than the Bank expected in June. This week’s figure should show an August rate of 4.6% or 4.7%, with the prospect of 5% when the September numbers are published in a month.

The governor will point to sharp rises in utility bills, roughly 30% for gas and 15% electricity (compared with a regulatory cap of 5% and 2%, respectively, in France), and the pass-through from oil’s summer peak of $147 a barrel. He will note food prices have continued to rise strongly, and in the official figures are up 13.7% over 12 months.

What he should also be able to say is that inflation is close to a peak. Though we will not know for sure for two to three months, a September inflation rate of 5% should be the summit, after which the rate will fall first gradually and then sharply.

That will be rather good news for state pensioners and others on benefits. Their annual uprating is based on September’s inflation rate, though on the retail prices index rather than the CPI (consumer prices index) targeted by the Bank. By the time that uprating comes through next April, inflation should be dropping rapidly.

How can we be sure of that? Oil deserves a column in itself but I will wait until it breaks decisively below $100 a barrel. Last week Brent crude dipped below that level, with the main US-traded oil, West Texas intermediate, also falling, prompting a cut in production quotas by the Organisation of Petroleum Exporting Countries (Opec). We have to hope this attempt by the cartel to stop prices sinking below $100 fails.

Figures last week showed output price inflation — measuring manufacturers’ price rises “at the factory gate” — fell from 10.3% to 9.7%, with core inflation sliding from 6.8% to 6.4%. Industry’s material and fuel costs last month were 26% up on a year earlier but this was down from the peak in June, when there was a rise of almost 31%.