Line profiles of C iv λλ1548–1551 and the best fit models (2σ) compared to the values of υ_∞ determined by spectral fitting (this work, red dotted line) and those of Crowther et al. (2016, yellow dashed line). The shaded regions indicate the 2σ errors on the derived υ_∞. We used the blue transition of the doublet (λ = 1548.19Å) for indicating velocities. We show profiles with different C iv λλ1548–1551 appearances: strong and saturated (top), strong but not saturated (middle) and weak (bottom). In all cases υ_∞ from spectral modelling lies bluewards of that of Crowther et al. (2016). See also Fig. 21.