Dundas first sat for the borough of
Richmond in 1774,
Orkney and Shetland from 1781 to 1784, Richmond again in 1784–1786, and finally for
Berkshire (UK Parliament constituency), which he represented in ten successive parliaments (1794–1832). He was, finally, the second eldest member in the house. He was a liberal in politics. In 1802, on the resignation of
Mitford (afterwards
Lord Redesdale), the then
speaker, he was nominated, by
Sheridan, as his successor in opposition to
Abbot. He, however, withdrew from the contest. Dundas was
Counsellor of State for Scotland to the
Prince of Wales, and
colonel of the White Horse volunteer cavalry. He was raised to the peerage as
Baron Amesbury, of Kintbury, Amesbury, and Barton Court in the County of Berkshire, and of Aston Hall in the County of Flint, on 11 May 1832. Apart from his political career he was also the first chairman of the
Kennet and Avon Canal Company and the
Dundas Aqueduct was named after him. ==Personal life==