Alexander McNab (1745-97)
Alexander McNab was born in Perthshire, Scotland. He joined the itinerancy in 1766 and laboured with great success in circuits across the country. He was well regarded by Wesley although with some concern over McNab's inabilty to accept criticism.
In 1779 McNab embarked on a tour of England to raise money to cover the cost of repairing the Edinburgh Chapel. While in Bath, he publicly disputed Wesley's right to invite the Anglican minister Dr Edward Smyth to preach in the Methodist Chapel. He argued that preachers were appointed by the Conference and that Wesley had no right to impose Anglican clergymen on them. It was only after a personal visit by both John and Charles Wesley that the defiance of his will by McNab and his supporters was ended. McNab was expelled from the Connexion but was reinstated in 1780, much to Charles Wesley's disgust.
McNab retired from the itinerancy in 1782 and ended his days as the pastor of an independent congregation in Sheffield, Yorkshire
Source: John Pawson, A Chronological Catalogue of all the Travelling Preachers (1795) and Luke Tyerman, The Life and Times of John Wesley volume 3 (1872), 303-313.