Mungo Ponton, who became a photographic inventor, lived at No. 6 for about two years between 1826 and 1828. He was probably related (nephew?) to Alexander Ponton who also lived there at the time. Born at Balgreen, Edinburgh, on 20 November 1801, he was admitted to the Society of Writers to the Signet on 8 December 1825. He was a founder and later secretary of the National Bank of Scotland. Ill-health caused him to give up a professional career, and about 1845 he moved to Bristol for a milder climate. He died there on 3 August 1880.
On 20 June 1834, Mungo Ponton became a Fellow of the Royal Society of Edinburgh. In 1838, the Society of Arts for Scotland awarded him the silver medal for his contributions to the development of the electrical telegraph. In 1839, he discovered the light-sensitive quality of sodium dichromate, a cheap and simple method of preparing photographic paper which advanced the production of permanent photographs. He presented his findings to the Society of Arts for Scotland on 29 May 1839 and published them in the Edinburgh New Philosophical Journal.
In 1845 the Society of Arts for Scotland again awarded him a silver medal, for his process for measuring the hourly variation in temperature of photographic paper. That year he also developed a variation of the calotype process to allow for shorter exposure times.
Mungo Ponton married his first wife, Helen Scott Campbell, on 24 June 1830, some two years after leaving Malta Terrace. The couple had seven children. Helen died on 7 August 1842. He married his second wife, Margaret Ponton (possibly related), on 7 November 1843 with whom he had a son. He married his third wife, Jean McLean, on 1 August 1871.