Mr. William Roscoe, however eminent he might be in civic virtue, was precluded from taking any part in the municipal affairs of the town, as he was not a freeman of the borough. Nor, for the same reason, was he able to exercise the Parliamentary franchise. But whilst he himself had no vote, there was nothing to prevent the voters from sending him to the House of Commons as their representative if he and they were so minded. In 1806 a swing of the political pendulum brought the Whigs into general favour, and the burgesses of Liverpool returned him at the head of the poll. By speech and vote he threw all his influence on the side of Clarkson and Wilberforce in their successful efforts to abolish England’s participation in the slave trade. Although those who sent him to the Legislature must have known his views on this subject, his constituents were highly incensed at his action in thus seeking to destroy, as they imagined, one of the chief sources of the prosperity of the town. Moreover, he had added to the enormity of his offence by speaking and voting in favour of Catholic Emancipation. Accordingly, a mixed and muddled mob of ardent Protestants and drunken sailors, crews of slave-ships, were gathered together in order to assail him on his return from Westminster at the close of the session. A riot broke out, but his friends had taken timely precautions, and he escaped without injury. But the House of Commons had few attractions for him. He resigned his seat, and nothing would induce him to seek re-election. He still maintained his interest in the political movements of the time, and became a busy pamphleteer, wrote in favour of the abolition of slavery as a logical consequence of the abolition of the slave trade; on Parliamentary reform; penal jurisprudence and the treatment of criminals; and on national education.