Hull you say? Home to one of the great universities.
At the moment self assessment only involves declaring income and realised financial gains. What's missing on a tax return is someone's net worth or wealth.
A good starting point is to get people to declare their net worth which means you'd be able to compare their effective tax rate (total tax payable divided by declared income) and their net worth. You'll find that the multi millionaires and billionaires' effective tax rates are way lower than normal working people which 'should' lead to greater scrutiny in their affairs i.e. how are they managing to do that. This is the case in many countries. Trump for example barely pays any income tax compared to his annual income and net worth. Undeclared income is a separate matter.
At the moment, all gains on the sale of a primary residence are tax free. Maybe it's time to start taxing this on gains of over say £250k (even at say 2%) because so much wealth is tied up in property that ultimately gets inherited.