In 1799, John Penn established an agricultural engineering business, near Deptford, specialising in mills for corn and flour.
The firm of John Penn and Sons of Greenwich from c.1830 was to develop into a famous marine engineering firm. Over the next twenty years they grew to be one of the major engineering works in London.
John Penn II was apprenticed to the firm, becoming a partner in the early 1830s. The firm went on to become a major engine supplier to the Royal Navy in the transition from sail to steam.
John Penn II married Ellen English in 1847, the daughter of William English, of Hunter and English millwrights, who installed the waterwheel at Lea Bridge in 1837.
 Greater London Industrial Archaeology Society August 2008 Book Review of ‘John Penn and Sons of Greenwich’, by Richard Hartree