Soane presented plans in June 1791 for altering the secondary entrance to the Rotunda. Taylor had built this entrance shortly after the east wing, 1765-1772. The main entrance to the banking halls and Stock Exchange was located on the east side, accessed from Bartholomew Lane, and was over-crowded with traders and therefore rendered somewhat useless. An understated doorway in the Front Court led to a simple rectangular corridor. Soane narrowed the corridor by inserting several small offices adjacent. The offices were intended for the Chief Clerks of the Three Per Cent Offices and the Accountant General of the Court of Chancery.
There is a later set of drawings for this vestibule, as significant alterations were carried out in 1814. Among the 1814 drawings are surveys of the existing vestibule, showing the design executed in 1791 (see 'Rotunda vestibule and Treasury, 1814-1815' scheme).