In Greek mythology Achilles was the son of Thetis, a sea-nymph. Here Thetis is shown dipping the newly-born Achilles into the river Styx, in the hope that the river's magical properties would protect him. Achilles became a legendary hero, but was killed by an arrow to his heel, the one part of his body left vulnerable.

This group was commissioned by Colonel Thomas Johnes and was originally displayed in his magnificent conservatory, at Hafod, Cardiganshire. Marine symbols are depicted around the base. The heads of the figures are portraits of Johnes's second wife Jane, and their infant daughter Mariamne. The plinth on which the sculpture sits is almost certainly original; interestingly it incorporates a cupboard. At a later date the original mahogany surface was given a painted marbled finish; one panel of this has been retained as a record of this later finish.

Thomas Banks (1735-1805) was apprenticed to a London mason, but also spent time working alongside the sculptor Peter Scheemakers (1691-1781). He enrolled in the life classes held at the St Martin's Lane Academy, and later at the Royal Academy Schools. In 1772 he became the first sculptor to win the Royal Academy's three-year travelling stipend, and went with his wife to Rome, where he eventually spent seven years. He specialised in ideal works, most of which were executed in Rome for British patrons, and he continued to produce similar work after his return to London. He was made a Royal Academician in 1786. Banks was one of the most original British neo-classical sculptors, infusing his work with the antique spirit rather than to a superficial classical style. He tried to establish a market for modern gallery sculpture, made specifically for individual patrons, as seen in the present sculpture.