Jeapes was born in Belfast in 1965. He was educated at Hampton Dene Primary School, Hereford, Little Chalfont Primary School, Lorraine Primary School, Camberley, Dumpton Prep School, and Sherborne School. He went to the University of Warwick.

Jeapes has written several books, all in the science fiction genre. His first full length novel was His Majesty's Starship, which concerns the actions of several Earth countries competing for the chance to start again on a new world.

His latest book, The New World Order, is set during the English Civil War, but provides an alternate history. Non-human forms from a parallel Earth come to England at the peak of the Civil War. The leader of the invading forces attempts to avoid inflicting suffering upon the English people, but soon comes under pressure from superiors who disapprove of his soft-footed approach.

His published titles are:

• His Majesty’s Starship (1998) - published as The Ark in the US in 2000
• Wingèd Chariot (2000) - published as Time's Chariot in the US
• The Xenocide Mission (2002)
• The New World Order (2004)

The two most recent books have been published by Random House, with the earlier books published by Scholastic Press.

Under the children's author name Sebastian Rook he has written the first three titles of the Vampire Plagues series:

• London (2004)
• Paris (2004)
• Mexico (2005)

(The remaining three Vampire Plagues titles - Outbreak (2005), Epidemic (2005) and Extermination (2006) - were written by Helen Hart.)

He also wrote a Doctor Who short story for Consequences.