Parliament was the only place where laws could be created or changed. Attempting to convince Members of Parliament to abolish a profitable trade would have to overcome two major hurdles:
The King, the Lords and MPs overwhelmingly supported the slave trade and the prosperity of the plantations up until the 1790s.
There were two reasons behind this support for the slave trade: Empire and wealth.
When considering whether they would vote against an abolition bill, a Parliamentarian might: