45% Income Tax + 9% Student Loan Repayment (mandatory) + 3.25% National Insurance Contributions

Gives 57.25%, but this is off because:

- Student loan repayments start somewhere above 20k, which decreases it

- National insurance runs at 10.25% before going down above a certain income, which increases it

- Higher rate and basic rate apply to some income (but no tax free allowance), which decreases it

Hence to a round(ish) number roughly 55%