From Dr Dirk Willem te Velde.

Sir, It is extremely helpful to open up the global discussion on the social contract between banks and society (“How we can restore trust in financial institutions”, Gordon Brown, November 9). Unfortunately, out of the four proposals, a transaction tax fails by definition one of four principles he has laid out; if it is not implemented globally it will not work, but if it is and if it worked, it distorts capital markets (for example pension and hedge funds, in addition to banks) in ways that might reduce global growth and social welfare.