Five companies linked to the late rice-cooker tycoon William Mong Man-wai's Shun Hing Group are suing the executors of his estate for more than HK$1 billion which they say they are owed. The companies said Mong took the money 'without proper authority' or that they had extended it in the form of loans between 2002, the year of his high-profile divorce, and 2010, when he died. Bank of East Asia chairman David Li Kwok-po and lawyer Vic Choi Fan-keung, the executors of Mong's estate, are named as defendants. Four firms that are part of the group - Shun Hing Holdings, Shun Hing Electronic Holdings, Shun Hing Electronic Trading and Shun Hing Technology - say in a High Court writ that Mong owed them HK$941 million. Liberian-registered Timmerton Company, which owns 40 per cent of Shun Hing Holdings, is seeking US$133 million, says a separate writ. Both writs were filed on Wednesday. A Shun Hing Group spokeswoman said the legal proceedings had been instituted by agreement between both sides. 'They are normal and reasonable legal proceedings.' The filings are the latest step in a long legal battle over Mong's fortune, which is said to be in the tens of billions of Hong Kong dollars. Last year, Mong's first wife, Serena Yang Hsueh-chi, their three daughters and two sons filed a writ seeking a court declaration on their entitlement to the Huge Surplus Trust and/or its assets. The trust owns 50 per cent of Shun Hing through its representative, Huge Surplus Limited. In April last year, Li and Choi applied to the court for direction regarding various claims by Yang; she and Mong's daughter Cynthia Mong Sien-yee; Mong's widow Wong Pui-fan; and Timmerton. Mong set up Shun Hing Hong in 1953 and used his father's business links with Panasonic to import Japanese goods. He struggled to sell the first eight rice cookers and went door to door to sell them. In 1965, he sold 88,000 and in 50 years he sold 10 million. He married Yang in 1958. Their 2002 divorce led to a legal dispute over HK$4.6 billion of family assets, which was later settled out of court.