Sikeano, dividends and other payments made by companies are usually paid net of tax of up to (I think) 34%. Previosuly pension funds were allowed to claim this tax back from the government.
In 1997 Gordon Brown changes the rules to prevent pension funds claiming this tax back, therefore effectively intorducing a tax on the income of pension funds.
When you consider the amount of money tied up in UK pension funds and the income this produces, the Treasury does very nicely out of the new rules.