While previous research on political interviews has concentrated on strategies of evasion and non-commitment, this paper aims to show that a complementary and equally important feature of interviewees' discourse is the use of modal certainty. An examination of modal selections in a British corpus of political interviews further reveals that the choices are functional and can be related to the speakers' aims, their position in the discourse and their affinity with the thesis. On a more theoretical level this paper aims to demonstrate that interpersonal meanings structure texts just as much as ideational ones and that macro-modalities contribute to coherence in important ways. Finally, it is argued that a fruitful analysis of modality in discourse must be based on the view that modal choices in a strict sense are closely linked with other choices expressing the speaker's intrusion upon the thesis.