In the weeks and months to come, we must find ways to rebuild trust. Yet trust in politics, once dented, is difficult to repair. And so, as the police investigate Peter Mandelson amid allegations of financial and political misconduct, indeed criminality, politicians have a herculean task to persuade people that they act in the public interest and not only self-interest. Already, two-thirds of the British public believe that politicians are out primarily for themselves. The grim truth is that unless something fundamental changes, this week’s revelations will be acid in our democracy, corroding trust still further.