Selected helium lines in the spectrum of VFTS 450 near quadrature; smooth red curves show gaussian fits to the data. Although these helium lines give consistent results for the primary (at ~+400 kms^-1), the secondary velocities are discordant (Sect. 3.1.2; for reference, the dashed vertical line indicates the measured secondary He iλ4471 velocity). This figure also illustrates the differences in He i:He ii line ratios in the two components (Sect. 4.2).