Anyone who has studied even basic economics will know that excessive profits are usually the result of an inefficient marketplace. So, let's stop all the whinging from the grossly overpaid people in the City and bring proper competition into the financial marketplace. Let's create small, innovative banks, like the life, widow and mutual societies that thrived in Victorian times: banks that are willing to lend and will work with far more sensible and contained equity ratios.
And let's ban derivative trading when it is leveraged. How can you buy more shares in a company than exist ? Worse still, how can you then use this to bet against the company since you effectively control the company despite owning no shares in it (a similar problem has beset the bond market and resulted in misery across the Eurozone).
The UK has done very well by being open in its approach to financial markets when other countries are not. The result is that the French government now control huge swathes of our utilities. We seem to neither have or cake nor be able to eat it.
You either believe in free, open markets or you don't. There's nothing in between.