LONDON (Reuters) - Rock legend Mick Jagger launched a surprise counter-attack in his divorce battle with Texan supermodel Jerry Hall on Tuesday when he alleged the couple had never been legally married. Hall, 42, launched divorce proceedings last Friday amid reports that 29-year-old Brazilian model Luciana Morad was expecting Jagger`s child. Now Jagger, 55, is insisting that the couple`s Hindu-style marriage ceremony at a woodcarver`s home on the Indonesian holiday island of Bali in 1990 was never legal because the correct papers were not filed. Hall`s divorce filing immediately prompted speculation that she was seeking a 30 million pounds ($50 million) slice of the estimated 145 million pounds fortune Jagger has built up over his nearly four decades in the rock business. Legal experts said Jagger`s move might save him a lot of money if he could prove the couple had never been married. But they also suggested the tactic might not win him much sympathy in court and could end up reducing his access to the couple`s four children. Hall could decide to sue for divorce in the United States, where she would be entitled to a half share of Jagger`s assets on the basis of having been in an established relationship with the singer. Hall and Jagger had been lovers for more than a decade before their marriage ceremony in Bali. Jagger was first married to former Nicaraguan model Bianca Perez-Macias in 1971. The marriage lasted six years, ending in a costly divorce. It was during the period when the relationship with Bianca was on the rocks that he started to see Hall. Asked last September what had changed during his 30 years as a pop star, he replied: "The slogan in the sixties was sex, drugs and rock `n roll. The slogan now is drugs and sex and rock `n roll."