Congratulations George on producing the most fundamentally flawed analysis of the impact of the 50p tax rate.
Apparently it didn't raise as much as was expected, because a lot of people took additional income in the preceding year to avoid it. So rather than waiting until we see what it produces this year (the first year that won't be available as an option to additional rate taxpayers) we're going to get rid of it.
Except we're not going to actually get rid of it, we're going to reduce it so it's only 5p different to the higher rate of income tax. I'm sure that will bring all those departed oligarchs and business leaders that fled the country rushing back.
Perhaps the money raised (five times the current income, apparently) can all be used to set up and run this new means testing system for child benefit?