When a proposal to cap the amount of tax relief that individuals can claim was included in the recent Budget, charities mounted a huge campaign against the changes. Hundreds of organisations have signed up to the 'Give it Back George' campaign, urging the Chancellor to rethink the plans.

The charities involved include some of Britain's biggest not-for-profits, along with many tiny local organisations, and groups of all sizes in between. Yet the reduced tax relief will only affect a small, elite band of charity donors - those who give more than £50,000 or a quarter of their yearly income.

Who are these big donors and why have charities been so vocal about saving their tax breaks? Simon Cox finds out more about wealthy charity backers, investigates the proposed changes and asks how much tax affects the motivations of Britain's biggest givers. If the Coalition proposals turn into law, how much does the Exchequer stand to gain - and how much do charities stand to lose?

Producer: Mike Wendling.