John and Elizabeth were the children of Bennett Barber of Hampton Wick. Elizabeth was born in 1729; she married Thomas Pewtress on 18 April 1752 and died at Northampton on 13 November 1786. John was a partner in Dimsdale's Bank, according to the label on the reverse of the portrait. He was also admitted a Member of Lincoln's Inn on 6 July 1741, and made the Grand Tour, visiting Rome between 1769 and '70. He died at Sion End.

A drawing by Hayman, dateable to the late 1740s, measuring 17½ x 12½in. is in the Fitzwilliam (see Francis Hayman, Kenwood exhibition, 24 June-30 September 1987, no.54); this drawing must surely be the preparatory sketch for the present painting. As Brian Allen points out in the catalogue entry for the drawing, portrait studies such as this by Hayman are rare, and give an intriguing insight into the artist's method of working. The portrait of John Barber can be compared to another of a slightly later date (c.1749-50) of George Dance the Elder (Hayman exhibition, no.20), also in the Fitzwilliam; here the sitter is again shown in a panelled room, leaning on the same type of chair, with an interlaced back, several of which it is known Hayman kept in his studio.

During the 1740s, Hayman was much involved with the St. Martin's Lane Academy, and the life surrounding Old Slaughter's Coffee House, the great meeting place of artists at the time; it was also one of his busiest periods of work, with commissions being undertaken for the Foundling Hospital, Vauxhall Gardens as well as theatrical subjects and society Portraits.