Who is The Marquis Richard Wellesley and the Earl Arthur Wellesley from Commodore Hornblower and what is their importance?

The Marquis Richard Wellesley, K.P., is the Britannic Majesty's Secretary of State for Foreign Affairs. He is Barbara's brother and Hornblower's brother-in-law. Wellesley is the ex-Governor-General of India and currently the Secretary of State for Foreign Affairs. As such, he keeps Hornblower informed about the political situation in the Baltic, and then delivers Hornblower's verbal and written orders.

Over the course of the novel, Arthur Wellesley leads the British military forces in Spain and inflicts heavy defeats upon the French occupying forces there. At the time of the novel, Spain has revolted against France's despotic rule.