In this paper, we discuss the effect of a strong perpendicular magnetic field component upon a range of coupled double quantum well (CDQW) devices. With increasing inter-layer tunnelling, we observe a transition from double- to single-layer characteristics in the magneto-transport data. The effect of the perpendicular field upon a CDQW has also been considered through a self-consistent Poisson/single-particle Schrödinger model. The implications of the experimental and theoretical results for the current analysis of the transport properties of CDQWs are discussed.