Catherine Zeta-Jones and Michael Douglas are to sue Hello! magazine for publishing "surreptitious" photographs of their New York wedding, after a landmark appeal court ruling yesterday gave strong backing to their case.

Lawyers said it was the first time the appeal court had stated emphatically that a right of privacy exists in English law. In what was seen as a test case, the judges said that the right protects both celebrities and ordinary members of the public.

The couple had signed a £1m deal with OK! magazine for exclusive pictures of their £1.2m wedding last month. But OK!'s rival Hello! hit the streets three days earlier with its own photographs, taken with a hidden camera.

OK! and the couple were too late to stop 15,750 copies already on sale, but won an injunction in the high court banning the rest of the 755,900 print run.

This was overturned on November 23 by the court of appeal, which yesterday gave its reasons for lifting the injunction. But the judges held that the couple were likely to prove at trial that publication of the photographs was a breach of confidence and violated their right to privacy.

Lord Justice Brooke said if they sued and succeeded, "The bill which Hello! will have to pay is likely to be enormous." Maninder Gill, group legal director of Northern & Shell, OK!'s publishers, said the damages claim still had to be worked out, but it might be for all the profits from that issue.

Lord Justice Sedley said the couple had "a powerfully arguable case".

The judges said they had had "misgivings" about lifting the injunction, but the general rule was that an injunction should not stand if damages can afford adequate compensation.