Although cataclysmic variables (CVs) come in a wide variety of shapes and sizes, the essential ingredients are a compact primary star and a Roche-lobe-filling secondary. In most cases the cool component is a main sequence dwarf, and the compact component a white dwarf (WD). Material from the cool component flows through the inner Lagrangian point via an accretion disc onto the surface of the WD; the flow near the WD is significantly affected by the strength of the magnetic field the WD may have (see Warner for a review of CVs). CVs are characterised by regular eruptions, ranging in energetics and frequency from ‘dwarf novae’, in which eruptions of amplitude ~3-4 mag in the visual occur every few days to weeks, to classical novae (CNe) in which the eruption is explosive, due to thermonuclear runaway (TNR) in material accreted on the surface of the WD (see Bode & Evans for a review of CNe).