There can be no question that it was a gross invasion of privacy to take pictures of the Duchess of Cambridge with a long-lens camera while she and Prince William were on holiday. No public interest defence could possibly apply in such a case, and Clarence House's condemnation of a French gossip magazine's decision to print the photographs as "grotesque" and "unjustifiable" is wholly legitimate.

The Closer editor's defence – that the snaps covering four pages and including several of the Duchess topless are "not in the least shocking" – is, perhaps deliberately, missing the point. And lawyers on behalf of the royal couple are, rightly, strenuously pursuing all possible redress.

Given that French law specifically protects individuals' privacy, there must be a good chance of success. But with the fines for breaching the rules so low, celebrity magazines routinely factor the cost into their plans, and with the photographs of the Duchess already published, the damage is done.

For all the criticism of the British press, it is notable that – so far, at least – all have chosen not to print the controversial pictures. Quite right. The most disturbing aspect of the affair is the parallels with the paparazzi's hounding of Princess Diana. More than anything, Closer's objectionable editorial decision cannot signal open season on the wife of her son.