John Wesley knew George Whitefield from the days of the Holy Club. Whitefield had had a similar conversion experience to the Wesleys a few years earlier, and had gone on to preach in large open-air meetings.
Wesley preached the first of his open-air sermons at Whitefield's invitation in Bristol in 1739. As an Oxford don and an ordained Church of England minister, Wesley had a reverence for the 'proper' places of worship and was uneasy about preaching in the open air.
But since many working class people often felt excluded from the churches, 'field preaching' became a key feature of the Methodist Revival. More and more preachers were trained, and either travelled around like Wesley, or remained 'local preachers'.
Wesley went on to spend his life travelling the country, preaching to crowds on village greens, at pitheads, wherever he could find people to listen. During his lifetime he travelled an estimated 250,000 miles and preached 40,000 times.
His sermons appealed to people's hearts and minds, and were experienced as deeply personal messages by those who listened. They reached many who felt alienated from the Church because of their emphasis on God's freely-given forgiveness and love for all.
Wesley's published Sermons became and remain the doctrinal standard of the Methodist Church.