Sumner Redstone has removed two long-time allies from the board of the trust that controls his media empire, setting the stage for a bitter fight that will pit the 92-year-old billionaire’s daughter, Shari, against his friend and lieutenant, Philippe Dauman. Mr Redstone’s empire spans CBS, the leading US broadcast network, and Viacom, which owns a portfolio of cable channels, including MTV and Comedy Central, as well as the Paramount Pictures movie studio. Mr Dauman, Viacom’s chairman and chief executive, has for many years been Mr Redstone’s most trusted friend. But he and George Abrams, another ally of Mr Redstone, were surprisingly removed by the billionaire this week from the board of the family trust that will manage Mr Redstone’s holdings after his death. News of their removal was first reported by Fortune. Their removal from the board, which will not immediately affect Mr Dauman’s position at Viacom, is a victory for Shari Redstone, a critic of Mr Dauman, and the vice-chairman of CBS and Viacom. She was the sole Viacom director earlier this year to vote against him succeeding Mr Redstone as chairman of the group. Viacom has been rocked by slumping audience ratings and declining advertising revenues. Its shares have fallen almost 40 per cent over the past year.