These designs for a chapel were intended for the eastern corner of James and William Streets in the north-west corner of the Adelphi complex. It was designed for Augustus Toplady (1740-78), who was the son of Major Richard Toplady, who had died of yellow fever in Cartagena in May 1741 when Augustus was a baby. Toplady was a scholar at Westminster School, attended Trinity College, Dublin, and in 1762 became a Calvinist clergyman of the Church of England. He was also a hymn writer, his most famous being the Rock of Ages. For the majority of his career, Toplady was vicar at Broad Hembury, Devon, but spent his last years in London.

Adam’s designs for Augustus Toplady’s Chapel were made in 1776, and it is not known if they were speculative, or if Toplady had commissioned the designs on his arrival in London. The designs were not executed, and instead Toplady leased a French Calvinist chapel in Orange Street, but died two years later in 1778 from consumption.

Rowan has likened the designs for Augustus Toplady’s chapel to a garrison chapel, being commodious and spare in ornament. Moreover, he notes the similarity of the façade to the Royal Society of Arts building nearby, with a Venetian window within a relieving arch above a tripartite porch, perhaps producing something of a specific Adelphi style.

A small Baptist chapel was built on the plot which had been offered to Toplady, but this did not make use of the same design, and there are no extant drawings of the scheme. This chapel was demolished by its neighbour, Coutts Bank, who purchased the building some years later in order to enlarge their own facilities.