Back in March, our price tracking showed food inflation at 3.1%. This was in marked contrast to one particular and highly selective study, but tallied almost exactly - indeed spookily - with figures from the major multiples.

In the past few weeks, however, our Grocer 33 data has shown a marked increase in prices across virtually every one of the 12 categories we track, showing double-digit inflation since the middle of May. In the meantime, supermarket CEOs have barely budged from their position that food price inflation is little over the overall rate of inflation. What's going on?

The mults measure inflation across the entire range of products, totalling 10,000-plus SKUs, which we sadly can't afford to do, and it could be that if you include cocktail sticks and all the other slow-moving lines, including extensive non-food ranges, the figures would drop.

Talking of non-food, Sainsbury's has done more than its rivals (albeit from a higher base) to control prices, up 7.8% this week versus Asda's, up 13.3% (albeit from a lower base). And one assumes Sainsbury's calculations for inflation haven't been made by downgrading to its value ranges, a practice which Justin King appeared to endorse earlier this month presumably to help shoppers control purse strings. But could it be, having got their results out of the way, and with favourable like-for-likes likely over the summer vis à vis last summer's dismal showing, that supermarkets are relaxing their iron-like grip?

Possibly. But as I've said here before, I believe it's the escalation in oil prices, and their impact on everything from fertiliser costs to distribution and heating, that's taken inflation away from commodity-based SKUs and into the mainstream.