Radial velocities of WASP-22 showing a linear drift in the systemic velocity of m s^-1 yr^-1. The colour and symbol key is the same as in Fig. 1. The Keplerian orbit of Table 3 was subtracted. The value of from Table 3 is plotted as a solid line, relative to JD = 2 455 013, which is the centre-of-mass of the RV data, weighted by the square of the measurement precision. The drift’s 1-σ error bars are plotted as dashed lines.