The British public has long enjoyed a fairly fulfilling love affair with the Sainsbury brand: through good times and bad, it has shown great loyalty and more recently Sainsbury's sales growth has been at the top end of the industry pecking order. But that is about to change: standards within the stores could be about to fall and Sainsbury's star may cease to be in the ascendant. The increasingly happy band of JS shoppers are not going to like it. Blame private equity.

In all honesty, I feel a bit sorry for the JS management squad (but only as much as anyone can feel sorry for a gang of soon-to-be multi-millionaires). A number of executive teams have tried and failed to rebuild the JS brand that faltered during the early 90s. No team has done as good a job as the present one.

But suddenly the rules have changed. In six months, Justin King and co will have a different agenda. They will either be out of a job, they will be working for whichever selection of private equity groups bids for JS, or they will be still public, but obliged to walk away from the successful sales-led recovery plan that they were following.

The obsession has to become profitability. Up until now, King has been right in arguing that in order to build a sustained recovery, the obsession would have to be sales growth: profitability would come later. The emergence of private equity means this obsession has to change: it's all about the bottom line, not the top line.

This has to be bad news for those loyal JS shoppers. For the last couple of years, the desire to make Sainsbury's a better place to shop again has been well received but now, in order to drive the bottom line, prices will have to go up (and a straw poll in the office suggests this is already happening).

Service levels will be lowered and investment in the brand through advertising will fall. Expenditure to build new stores will be virtually nil, and reinvestment in the existing chain will be kept to an absolute minimum. The brand will wither on the vine.

The best-case scenario for customers is that private equity walks away. King and co still have their sales targets after all. But private equity's shadow will always be there, ensuring that the bottom line remains paramount, and the customer and the healthiness of the brand come second. Sir Terry must be sleeping very soundly.