A radical change of tactics, which involved the introduction of a bill to ban British subjects from aiding or participating in the slave trade to the French colonies, was suggested by maritime lawyer James Stephen. It was a shrewd move, since the majority of British ships were now flying American flags and supplying slaves to foreign colonies with whom Britain was at war. A bill was introduced and approved by the cabinet, and Wilberforce and other abolitionists maintained a self-imposed silence, so as not to draw any attention to the effect of the bill. The approach proved successful, and the new Foreign Slave Trade Bill was quickly passed, and received royal assent on 23 May 1806. Wilberforce and Clarkson had collected a large volume of evidence against the slave trade over the previous two decades, and Wilberforce spent the latter part of 1806 writing "A Letter on the Abolition of the Slave Trade", which was a comprehensive restatement of the abolitionists' case. The death of Fox in September 1806 was a blow, but was followed quickly by a general election in the autumn of 1806. Slavery became an election issue, bringing more abolitionist MPs into the House of Commons, including former military men who had personally experienced the horrors of slavery and slave revolts. Wilberforce was re-elected as an MP for Yorkshire, after which he returned to finishing and publishing his "Letter", in reality a 400-page book which formed the basis for the final phase of the campaign.