In February 1405, Owain negotiated the "Tripartite Indenture" with Edmund Mortimer and Henry Percy, Earl of Northumberland. The Indenture agreed to divide England and Wales among the three of them. Wales would extend as far as the rivers Severn and Mersey, including most of Cheshire, Shropshire and Herefordshire. The Mortimer Lords of March would take all of southern and western England and the Percys would take the north of England. R. R. Davies noted that certain internal features underscore the roots of Glyndŵr's political philosophy in Welsh mythology: in it, the three men invoke prophecy, and the boundaries of Wales are defined according to Merlinic literature.