James Murdoch has signalled plans to have "precisely zero" involvement in his family's remaining businesses following the sales of 21st Century Fox and Sky, in a historic split of the world's best-known media dynasty.

The comments to friends inform a new book, The Battle for Sky, which chronicles the rise of Britain's dominant pay-TV operator and the struggles of the Murdoch family to gain full control over it.

The book describes how James and his father Rupert Murdoch, now 88, quashed opposition from his elder brother Lachlan to break-up and cash in a global entertainment empire built over three