The comments section was especially interesting, as usual. A lot of people concerned about whether there should be parity between the pay of rubbish collectors and hedge-fund traders (hmm, I wonder which one refers to drama professors, female or not, in that analogy), completely missing the point about pay scales.
Most people outside UK academia don't understand about the spine and the pay scales (look at all the questions we get about the pay scales here ;-).
Where I suspect the Professor at RHUL went wrong is that she was so conditioned by the spine point plus COL a year (plus the fact that she's a woman, and women just don't ask) that she forgot that the professorial scale is a complete free-for-all above the entry point.