The officer's mess was more than just a dining area, it was also a form of club that was the centre of the officers' social activities, particularly those of the bachelor officers. Mess dinners, which all bachelor officers were encouraged to attend, were held four or five nights a week. Married officers were only expected to attend once a week. The food served was of much higher quality and quantity than that served to the other ranks.

Each regiment's mess had its own traditions and rules. Some rules, however, were standard: for instance, all regiments passed wine from right to left (there was a superstition that a ship would sink within the year if the opposite was done), and all were forbidden to discuss women, religion and politics.

The doorway at the end of the mess is the only original door in this wing, in order to allow communication between the mess and the messman's room. The other doors were cut during the restoration of the fort between 1936-1938.