The Reverend John Louis Petit (1801–1868) was a leading writer and speaker on church architecture, who was one of the founders of the British Archæological Institute at Cambridge, a Fellow of the Society of Antiquaries, and an honorary member of the Institute of British Architects. The many beautiful watercolours of churches that he brought back from his travels, to Europe and the Middle East as well as all parts of the UK, were made to accompany his lectures and writing.

In the mid-19th century church architecture and restoration were controversial topics. Petit’s first book, Remarks on Church Architecture (1841), argued against the prevailing tendency to use the neo-Gothic style exclusively in restoring churches and building new ones. With examples collected from across the UK and the continent, Petit argued for the beauty of all historical styles.

Petit never sold his art in his lifetime. His work differs from that of commercial artists in that it is not contrived or artificially picturesque: through accurate sketches made in situ, he demonstrates the beauty of ancient churches from many different architectural traditions, arguing that no one style should be arbitrarily raised above all the others.

Petit's work has until recently been largely overlooked. A 2022 book on the artist by Philip Modiano was described by the art historian and critic Andrew Graham-Dixon as marking 'the rediscovery of a more or less completely forgotten master—an artist whose work, particularly in the medium of watercolour, reaches the highest peaks of innovation and virtuosity, worthy of comparison with that even of Turner'.