John Spyers appears to have started as a nurseryman, possibly working in his father's or uncle's business. Referred to as 'Mr Spyers', one of them supplied trees to Horace Walpole for Strawberry Hill in November 1748 and prepared a survey of the place in 1750. In 1765, John was engaged, together with Samuel Lapidge, by Capability Brown to assist with the preparation of garden designs at Hampton Court. He was already associated with Brown, being described as 'Mr Brown's surveyor', working at Tottenham Park in 1764. When he died, in 1798, he was described as 'Surveyor of Hampton Court'.
His work at Hampton Court is marked by two volumes of drawings of the Palace which have recently been rediscovered in the Hermitage store at St Petersburg and which were originally acquired by Catherine the Great. We must assume that they were sold at roughly the same time as Sir Robert Walpole's collection of Old Masters paintings in 1779. The Hermitage list the collection of Hampton Court watercolours as numbering 149 in total, marking this similar work as a rare example by the artist of Capability Brown's vision of the environs of Hampton Court.