He was a protégé of an important British politician, Henry Bilson Legge, who was three times Chancellor of the Exchequer.
Martin, although he lacked major political talents and was mistrusted by Thomas Pelham-Holles, 1st Duke of Newcastle, had a capacity for hard work and dealing with administration.
When Legge was restored to the Chancellorship for the third time in July 1757, Martin was the only person who had gone out of office in April who was not given a new job in the Pitt-Newcastle Coalition.
Having failed to obtain an office in the King's service, Martin was compensated by being appointed Treasurer to the Princess Dowager of Wales Augusta of Saxe-Gotha (mother of the future King George III of the United Kingdom) in October 1757, an office he retained until 8 February 1772.
The Times of Wednesday 26 November 1788 reported: "Last week died Samuel Martin Esq[2] a gentleman well known in the political world and particularly from his having fought a duel about five and twenty years ago with Mr Wilkes".