volver
So. If the government of the day decided on a 90% rate of tax for every penny earnt over than £50,000, and a 95% tax on any dividends, and a 98% tax on share income. Plus a 75% inheritance tax.
And they'd got elected on that manifesto.
Would that be appropriate?
I seem to recall that in the 1960s, or thereabouts, there was a 90% tax rate on the rather wealthy...
Not easy to find information, but:
in 1973 higher rates kicked in after £5,000 pa = £42,278 today. Basic rate = 30%
Highest rate of 75% kicked in at £20,000 pa = £169,000 today
Not sure if those figures are gross or net of tax allowances.
A bit similar to volver's suggestions, really 
It was Thatcher who decided that income tax rates should be lower and more tax was to be raised from VAT and NI. Her decision obviously hit the poorest the most as the percentage of their income paid in taxation is always higher than that of the wealthy (so it wasn't really a give away for most people, she just increased taxation from other sources.)
Thatcher was much attached to the 'trickle down' theory of wealth, but mostly wealth seems to have trickled up over the past 4+ decades...