Martha Marcy (1713-1800) married John Soan, a bricklayer, in 1738, and gave birth to 8 children, of whom the youngest was John Soane.
For this picture Sir John Soane's mother was, at the age of 84, having her portrait painted for the first time. The portrait was exhibited at the Royal Academy the year it was painted. Her resemblance to her son adn indeed her grandson John is very evident. She is dressed in black (she was a widow) but wearing a white mob cap, a kerchief around her neck and fine fawn leather(suede) gloves. In her later years she lived at Chertsey where Soane and his wife Eliza were frequent visitors.

Soane recorded the death of his mother in his Journal 4 (f.215) on 30 January 1800 writing Poor Old Lady died this day at 10 o’ clock in the Eveng in her 87th year and without a groan! On the next page he recorded giving a present of £5 5s on February 3rd to 'Mr Summers the Apoth. [apothecary] at Chertsey', presumably a thank-you for the care he had given his mother.

There is no known portrait of Soane's father, John Soan (1714–1768). In 1784, some time after his father's death, Soane changed his surname to Soane, adding the last 'e' as part of a deliberate programme of self-improvement.

J. Soane, Description, 1832, p.xii
Helen Dorey, 'The Historic Framing and presentation of watercolours, drawings and prints at Sir John's Museum', in ed. Nancy Bell, Historic Framing and Presentation of Watercolours and Prints, Proceedings of the Conference of the Institute of Paper Conservation June 1996, pp. 20-31