Here be Dragons by Sharon Kay Penman (Paperback)

An absorbing historical novel of power and betrayal, loyalty and political intrigue in thirteenth-century England, Wales and France, centring on King John of England, younger brother to the brilliant Richard Lionheart, Joanna, his illegitimate but recognised daughter and Llewellyn Ab Iowerth, Prince of Gwynedd, a bitter opponent of English ways, laws and encroachment into Wales who becomes Joanna's husband.