Asymmetries are a ubiquitous feature of the scrape-off layer (SOL) and divertor plasmas in any tokamak and are thought to be driven primarily by a variety of drift flows, the directions of which reverse with reversal of the main toroidal field. The understanding of precisely how these field dependent drifts combine to yield any given experimental observation is still very much incomplete. A recent campaign of reversed field operation at JET designed to match a variety of discharges to their more frequently executed forward field counterparts has been executed in an attempt to contribute to this understanding. This paper summarises the most important findings from these experiments and includes some new EDGE2D simulation results describing the SOL flow. (c) 2004 Elsevier B.V. All rights reserved.