It depends on a few factors. The easiest one is the age of senior officers. Once admirals and senior post-captains retire or die off, everyone moves up a step on the seniority list. Remember: once made post, you cannot jump another captain on the list of seniority. Now, you may have influential friends or be more popular with the able seamen or have the kind of flair that captured the imagination of the British population. With that kind of status, you might have access to better ships and stations. Next, the political climate (war vs peacetime) is important. If senior captains are wounded, killed, lost, captured, or removed from command, your odds of a better posting increase and your seniority will be greater. So, during wartime, a less senior post-captain would have more chances of advancement up the list.

There are two books I keep next to my collections of the O’Brian and Forrester books: a dictionary of Napoleonic era naval terms and O’Brians “Men-of-War: Life in Nelson’s Navy.” It is fairly brief with excellent illustrations. On pages 37-54 he tracks the life of a theoretical officer from midshipman to Admiral of the Fleet. Once made post, his model officer spends many years on frigates and ships-of-the-line before achieving flag rank. Even then, some admirals of the yellow get half-pay shore duty and it’s difficult to get rear-admiral of the blue.