London's first large factory was the Albion Flour Mill at Blackfriars Bridge. William Blake lived nearby and may have been inspired to coin the famous phrase "dark satanic mills" in his poem "Jerusalem". However, the mill was operational for only five years, from 1786 to 1791, before being destroyed by fire.
The Albion Mill, Blackfriars Bridge, etching, unknown artist; source: The New London Magazine VI (July 1790), p. 329.