What’s really wrong with pictures of the Duchess of Cambridge shopping?

The celebrity magazine Heat has published the following apology:

In our issue cover-dated 3-9 December 2011, we published a photograph of the Duchess of Cambridge, taken while she was shopping in a store. We now accept that we should not have done so, and apologise to her for our actions.

It is said that the PCC negotiated the apology after a complaint from the Duchess’s lawyers alleging harassment and intrusion. There has been no adjudication by the PCC, but the negotiation of an apology implies that Heat considered (or was persuaded) it was in the wrong.  But what’s wrong with publishing a picture of the Duchess of Cambridge shopping? It would not necessarily have been actionable as a misuse of private information. Inoffensive pictures taken in public places are low-level intrusions and do not necessarily merit legal protection. If the Duchess had been pestered or followed, she might have had a case of harassment. But in the absence of harassment, and accepting the danger of commenting on a case without full knowledge of the facts, her case may suggest that the PCC now expects more of publishers than do the courts.