5 GHz radio luminosity against bolometric luminosity for the UCHIIs with fitted SEDs, shown with circles. A sample of confirmed ionised MYSO jets by Purser (2017) is also included (indicated by diamonds). The dash-dotted line marks the expected radio luminosity from Lyman continuum emission. The dotted line shows the empirical relation extrapolated for low-mass YSO jets (Anglada 1995). The angular size of all sources is colour-coded and emphasized through the marker sizes (the jet sample marker sizes are exaggerated, as their resolution is higher).