The passage of Catholic emancipation in April 1829 was resisted, in the name of the inviolability of the Protestant Constitution, by a group of ‘ultra’ anti-catholics.1 The principles and personnel of this group have already been well described, 2 but its political activities have been inadequately explored. Since 1824, when they criticized Lord Liverpool's Government for dilatoriness in prosecuting O’Connell's Catholic Association, these ultras had tended to form a distinct group on the right wing of the anti-catholic Tories, and had been the most aggressive opponents of Canning's short-lived ministry in 1827. The emergence of an Irish demand for Catholic emancipation, of unprecedented force, was shown in O’Connell's victory at the County Clare by-election in July 1828 and in the ensuing months. This produced a determined resistance by the Irish anti-catholics, which had its counterpart in a British no-popery movement led by the ultras. Most of the leading ultras were peers, and the most prominent among them were the dukes of Cumberland and Newcastle, the marquess of Chandos, the earl of Winchilsea and Lords Colchester and Kenyon. For nine months before the passage of the relief bill they sought to counteract the immense fervour of the Irish Catholics by stimulating the ingrained anti-catholic feelings which had characterized the English masses since the sixteenth century. Their efforts, however, were of no avail against Wellington's decision to carry a Government emancipation measure. It is the object of this study to investigate the no-popery movement and to account for its failure.