William Essex trained as an enamel painter in the workshop of Charles Muss (1779 – 1824), Enamel Painter to William IV. Essex first exhibited at the Royal Academy in 1818 and throughout the 1820s and early 1830s built up a successful practice, working chiefly in enamel. William Essex must have had his first introduction to court circles through Charles Muss. He may initially have worked in collaboration with his teacher, but by 1827 was earning his own commissions from George IV. In 1834 Essex painted an enamel miniature of Charlotte, Duchess of Northumberland, governess to Queen Victoria, after Sir Thomas Lawrence; although he was already well established in royal circles, his patronage by the Duchess of Northumberland may have been an additional factor that contributed to his appointment as Enamel Painter to Queen Victoria in 1837 and Enamel Painter to Prince Albert in 1841. Queen Victoria employed Essex to make numerous enamel copies of portraits of her after Franz Xaver Winterhalter, which were set into bracelets and distributed as gifts. He also made numerous copies of portraits of her relatives and contemporaries. Most of these were commissioned within the same year as the original on which they were based, and were often given by Queen Victoria to Prince Albert. He also made historical copies of early miniatures and portraits at Windsor. Despite Essex's ostensible success, however, he fell into poverty in his later years and was forced to request that the Queen supplement his artist's annuity of £40 with a pension.

An inscription on the frame states that the enamel is by Essex after Jagomann and gives the date of the image as 1810. However, the full-length prototype by Ferdinand Jagermann (1780 – 1820) in the Veste Coburg is dated 1814. A half-length version of the same type is in the Royal Collection (404673) and another is at Versailles (MV 4591).

Prince Frederick Josias of Saxe-Coburg-Saalfeld, second son of Francis Josias, Duke of Saxe-Coburg-Saalfeld, and Anna Sophia of Schwarzburg-Rudolstadtt, was brother of the reigning Duke Ernest Frederick of Saxe-Coburg-Saalfeld and uncle of Francis, Duke of Saxe-Coburg-Saalfeld, grandfather to Queen Victoria and to Prince Albert.

Signed, dated and inscribed on the counter-enamel in black paint: Field Marshal / Prince Frederic Josias / of Saxe Coburg Saalfeld / Painted by Jagomann 1810 / Painted by W. Essex / Enamel painter to Her Majesty / & H.R.H. Prince Albert / 1848.