Not all parliaments are subject to Freedom of Information (FOI), and no one has studied what difference it makes to the working of a parliament. This article evaluates the impact of FOI on the UK Parliament by reference to its main objectives. It finds that FOI has made Westminster slightly more open and accountable; but it has not increased public understanding, participation, or trust. Westminster was already very open and other initiatives have helped increase participation. Trust was badly damaged by the MPs’ expenses scandal, triggered by FOI requests. The House of Commons’ hesitant response to those requests revealed problems of corporate governance.