This is really interesting. So, at the bottom of the SL scale, I'm paying 40% income tax on some proportion of my salary but 1% of some other proportion for NI?
Cool.
Yup.
Also, I have now read the dense and unwieldy prose of Her Majesty's Commissioners of Revenue and Excise more carefully.
You start paying NI contributions at the same level that you start paying tax. So it's 11% at £97 per week and upwards.
Effectively you pay 1% NI on all earnings above the tax threshold. But for earnings above the tax threshold and below 33,450 you pay 10% on that section alone. Yes, this is horribly regressive on low and middle earners, but NI was thought up in a time when the really wealthy weren't employees.
It's a great incentive to sit carefully at the top of the lecturer/bottom of the senior lecturer scales, because you really notice the difference once that 40% starts biting.