Lyman-continuum photon rate versus the corresponding bolometric luminosity for the 200 CORNISH H ii regions with Herschel/Hi-GAL counterparts studied by C2015. The spectral types indicated at the top are computed under the assumption that L_bol originates from a single ZAMS star. The red solid line denotes the N_Ly–L_bol relation expected if the H ii regions were powered by single ZAMS stars (see C2015). Note that 67 objects (~34% of the sample) lie above this line. The error bars in the bottom right corner correspond to a 20% calibration uncertainty.