The son of Robert Oastler, he was born in Leeds on 20 December 1789 and is said to have been blessed by John Wesley on his last visit to Yorkshire. Educated at the FulneckMoravian school, after some training as an architect, in 1810 he became a commission agent for Leeds wholesalers in their trade with the West Riding shopkeepers. In 1816 he married Mary Tatham, daughter of a leading Methodist in Nottingham. He began preaching, but became bankrupt in 1819. In 1820 he succeeded his father as steward of the Fixby Estate, left Leeds in 1821 and emerged as a Tory-Anglican factory reformer, becoming known as 'the Factory King'. His letter on 'Yorkshire Slavery', written to the Leeds Mercury on 29 September 1830, is seen as marking the start of the campaign for factory reform. His opposition to the new poor law led to his losing his stewardship and eventual imprisonment for debt in 1840-1844. From 1845 he lived in retirement in Guildford. He was a close friend of J.Raynor Stephens and Michael T. Sadler. He died in Harrogate on 22 August 1861.