Being solely ambitious of attaining to the bench, he refused many cases, especially those which involved writing papers, and took only such work as seemed to lead to advancement.

Through the favour of the Carteret administration, he was appointed Solicitor General for Scotland on 11 August 1742, and, no change occurring in the Scotch department on Lord Wilmington's death, held that post through the arduous and responsible times of the Jacobite plots and the rising of 1745.

[1] On 16 August 1754, Dundas was appointed Lord Advocate, having been returned for Midlothian unopposed on 25 April at the general election.

While in parliament, he opposed the establishment of a militia in Scotland, and, as lord advocate, was largely occupied in settling the new conditions of the highlands, and in disposing of his great patronage so as to enhance the family influence.

He was the best lord president who had filled the office, short but weighty in his judgements, thorough in his grasp of the cases, indignant at chicane, a punctilious guardian of the dignity of the court, a chief who called forth all the faculties of his colleagues.