He was educated at Cheam and at Leipzig University, and in July 1797 was appointed a junior clerk in the Treasury. He was soon promoted to the Revenue Department.
In 1801 he became private secretary to Nicholas Vansittart (Lord Bexley), who was then joint secretary to the Treasury; and in 1804 he drew up a pamphlet titled A Reply to Some Financial Misstatements in and out of Parliament in defense of the government. He became private secretary to Spencer Perceval after the latter became chancellor of the exchequer in the second government of the Duke of Portland (1807-1809).
He also filled a number of posts, most obviously that of assistant to Wellesley-Pole, later the third Earl of Mornington, who had been appointed chancellor of the Irish exchequer in 1811. Herries was appointed commissary in chief in October 1811, in which post he was responsible for raising money for Wellington’s armies and for negotiating financial treaties with the allies in Paris in 1814. When that appointment came to an end, in October 1816, Herries was given a pension of £1,350 per year, which was later reduced to £1,200. For the next seven years he filled a number of posts that demanded his financial skills.
In February 1823 he was elected as M.P. for Harwich in a parliamentary by-election and was appointed financial secretary to the Treasury by Lord Liverpool. His financial expertise paid off in 1827, when he was appointed chancellor of the exchequer in Viscount Goderich’s shortlived ministry (August 1827-January 1828), becoming a member of the Privy Council in the process. A conflict between Herries and Goderich on one hand and William Huskisson on the other, over the appointment of a chairman to the finance committee, led to the early collapse of the Goderich ministry and its re-placement by a ministry led by the Duke of Wellington. In the process, Herries was moved to the post of master of the Mint. He served briefly as president of the Board of Trade in 1830, until Lord Grey’s Whig ministry forced the Tories out of office.
He was also secretary at war in Sir Robert Peel’s ministry of December 1834 to April 1835. However, his career was by now an extremely checkered one. He retired from the Harwich seat in June 1841 and was defeated in his contest at Ipswich, remaining out of both Parliament and government office until 1847, when he was returned for Stamford as a Tory protectionist. He then gained office as president of the Board of Trade in Lord Derby’s government (February to December 1852). However, he retired from Parliament the following year.
He was married to Sarah, daughter of John Dorington, clerk of the fees of the House of Commons, on 8 February 1814. Until 1823 he was effectively a talented financial administrator married into an administrative family.