Nearly all of the drawings Soane presented to the Bank's directors on 24 November and 6 December 1791 included the proposal to heat the hall with a large central stove surmounted by a column-flue rising up to a radial vault supporting the lantern ceiling above the crossing. Taylor's existing hall was probably warmed by perimeter fireplaces, leaving the central public space underheated.
As Summerson has suggested, the idea for a central stove surmounted by column-flue at the Bank Stock Office may first have been Dance's, whose margin sketches in the survey drawing dated 19 November 1791 (drawing 1) show both the plan for a triple-fireplace stove and an ornate capital for the column-flue, and several of whose independent (December 1791) studies for the hall also include a column-flue (drawings 60-63). Central columns and radial vaults could be found in numerous medieval chapter houses, for example, at Wells and Salisbury.
The first three drawings represent the first stage in Soane's triple-lantern scheme and prefigure nearly all the main elements of the renovated hall: a three-bay centre-aisle; barrel-vaulted side aisles linked through arches; a square crossing surmounted by a circular lantern dome carried on pendentives; and floor space divided into public and working areas by circumferential counters running between four piers. However drawings 5-8 replace the lanterns on the end-bays with clerestory lighting.
Soane's preliminary designs continued to include a column-flue at least until March 1792. In the earlier drawings the column-flue appeared as a Greek Doric order, but thereafter took on a more Tuscan appearance (drawings 5-6) with one design showing spiral ornament up its shaft (drawing 7).
The design of the column-flue itself, however, is not a primary concern in any of the later drawings from c. January through March 1792 (drawings 5-8). Rather, the interest is in Soane's exploration of various decorative, proportional, and structural possibilities. The exploratory nature of these drawings makes them difficult to place in strict chronological order.
The last dated drawing including a column-flue is from 18 March 1792 (drawing 7). The first dated drawing omitting the column-flue is from 10 March 1792 (drawing 12). However, a wood and copper model of the Bank Stock Office, dated to February 1793, still included a hole in the lantern roof for the column-flue's chimney (Soane Museum, MR 20). This suggests either that Soane may still have been leaving open the option for a column-flue just months before the hall was finished in July 1793 (a possibility supported by the column-flue lightly sketched into drawing 16, a longitudinal section showing the hall as built); or that this model has been misdated and is actually one of several others mentioned in the records.
In the executed hall, a modified version of the central stove was maintained, but the column-flue omitted in favour of flues built into the hall's north wall (drawings 45-47).