Cosmic string power spectra used in this analysis: NAMBU (black dashed), AH-mimic (blue dotted) and AH (red solid). The spectra have been set to equal power at ℓ = 10. When normalised to 850 μK at ℓ = 10 they correspond to string tensions of Gμ/c² = 1.17 × 10^-6, 1.89 × 10^-6 and 2.04 × 10^-6 respectively. Note that the limits discussed in this paper mean that the CMB spectra presented here are less than 3% of the overall power spectrum amplitude and hence the differences observed at high ℓ do not have a large effect.