Orbital fit for J0218−31. Top panel: transit photometry from CTIO in g′ (blue), r′ (red), i′ (cyan) and z′ (green) with best fitting models shown in black. Upper-middle panel: phase-folded WASP lightcurve. Lower-middle panel: drift-corrected radial velocity measurements from CORALIE with best fitting model plotted in red, along with residuals. Bottom panel: drift-corrected radial velocity measurements during transit (the Rossiter–McLaughlin effect; black) with the best fitting model (red). Error bars have been omitted for clarity.