Porteus made a huge contribution and eventually turned to other means of achieving his aims, including writing, encouraging political initiatives, and supporting the sending of mission workers to Barbados and Jamaica.Deeply concerned about the lot of the slaves as a result of the reports he received, Porteus became a committed and passionate abolitionist, the most senior cleric of his day to take an active part in the campaign against slavery.He became involved with the group of abolitionists at Teston in Kent, led by Sir Charles Middleton, and soon became acquainted with William Wilberforce, Thomas Clarkson, Henry Thornton, Zachary Macaulay and other committed activists.In view of his passionate involvement in the anti-slavery movement and his friendship with other leading abolitionists, it was especially appropriate that, as Bishop of London, he should now find himself with official responsibility for the spiritual welfare of the British colonies overseas.During much of the following[clarification needed] 20 years – a time of national and international political upheaval, Porteus was in a position to influence opinion in the influential circles of the Court, the government, the City of London and the highest echelons of Georgian society.Porteus did this, partly by encouraging debate on subjects as diverse as the slave trade, Catholic emancipation, the pay and conditions of low-paid clergy, the perceived excesses of entertainment taking place on Sundays—and by becoming a vocal supporter of William Wilberforce, Hannah More and the Clapham Sect of evangelical social reformers.He was a well-known and passionate advocate of personal Bible-reading and even gave his name to a system of daily devotions using the Porteusian Bible, published after his death, highlighting the most important and useful passages; and was responsible for the new innovation of the use of tracts by church organisations.After a gradual decline in his health over the previous three years, Bishop Porteus died at Fulham Palace in 1809 and, according to his wishes, was buried at St Mary's church, Sundridge in Kent – a stone's throw from his country retreat in the village – a place to which he had loved to retire every autumn.His legacy lives on, though, in the fact that the campaign which he helped to set in motion eventually led to the transformation of the Church of England into an international movement with mission and social justice at its heart, appointing African, Indian and Afro-Caribbean bishops and archbishops and others from many diverse ethnic groups as its leaders.