Going through the second door on the West wall you will find yourself in the room of a junior officer, probably who is moving into his room. Most officers came from the upper and middle classes of British society because being an officer was an expensive proposition. Officers had to pay for their own food and equipment whereas the men did not. In addition, officers in the infantry and cavalry had to purchase their own commissions at a cost ranging from 450 to 9,000 pounds sterling: this was between three and twelve times their annual salaries. Royal Engineers and Artillery officers did not have to buy their commissions but they had to attend the Royal Military Academy at Woolwich in order to qualify.

A few common soldiers were promoted to officer rank for merit however this usually only occurred in wartime. In 1870, the "purchase system" was abolished but the vestiges of the system persisted until the First World War.