In both The Secret of Flirting and The Risk of Rogues I mention that Hart sold his commission. In case you don’t know what that means, during the Georgian, Regency, and partway through the Victorian periods, the British army (but not the British navy, apparently) used a system by which gentleman could buy a commissioned officer rank, beginning at cornet or ensign, and then purchase commissions to rise in rank (up to the rank of colonel). These commissions weren’t cheap, by any means (go to this page about officer’s commissions to see the costs). A commission as a cornet cost 450 pounds in 1837, which is equivalent to 38,000 pounds now ($50,473.88). And you can well imagine how much it cost to become a major. So Hart, a younger son of a rich marquess, could easily go up the ranks to captain. That’s why you always hear about younger sons of rich men going into the military. Once they decided to retire, they could sell their commissions for the total amount of money they spent and have a nice nest egg. That’s what Hart did. It’s more complicated than I’m making it sound (some regiments, like the Royal Artillery, used merit for advancement, and there were other restrictions), but this is the system in a nutshell. Now you know why some of those officers were so young (and incompetent).