Mel Gibson's wife files for divorce

It was supposed to be the happiest marriage in showbusiness, lasting almost 30 years and producing seven children. But after months of speculation, Mel Gibson's wife has launched what could end up being one of Hollywood's most expensive divorces.

Robyn Moore filed for divorce in Los Angeles Superior Court yesterday, citing "irreconcilable differences" for the breakdown in her relationship with the Oscar-winning star, whom she married in 1980 when he was an unknown Australian actor.

The couple, who face a battle over Gibson's personal fortune, estimated at $900m (£600m), and the fate of their son Tom, 10, issued a joint statement making a somewhat ambitious request for privacy, after Ms Moore's lawsuit was published by the showbusiness website TMZ. "Throughout our marriage and separation we have always strived to maintain the privacy and integrity of our family and will continue to do so," they said.

It was not clear how long the couple, who are both devout Catholics, have been separated but a report on the US television show Entertainment Tonight claimed they had been living apart for almost three years.

Ms Moore's decision to formalise their separation may have been prompted by the fact that last month, newspapers published pictures of a topless Gibson, 53, embracing a bikini-clad young woman on the beach near his holiday home in Costa Rica.

The case comes at an inconvenient time for Gibson, who is about to mount a comeback with the release this November of Edge Of Darkness – his first major Hollywood film in almost five years. His career went seriously off the rails following his arrest for drink-driving in Malibu, California, in 2006.