In Paine’s original design, there was no communication between the card and the tea room except by passing along the landing in front of the banqueting room, or ballroom. The construction of a new dining room to the rear of the building in 1806 would have made this inconvenient, and in 1864 the last significant alteration was made to the Mansion House.
This was the introduction of a gallery behind the staircase. This allows direct access between these two rooms and, by providing an alternative means of circulating, prevents congestion on the landing. The new feature was designed to fit sympathetically into its context and only details in the glass of the roof-light readily identify the work as Victorian. The design was the work of William Butterfield, the borough surveyor and was carried out in 1861. The original Venetian window in the rear wall over the staircase was removed but the design was copied in the new external wall. The window was renewed and the glass replaced in 1986 by the new panes of stained glass, specially-commissioned from Harry Harvey of York, to commemorate the International Year of Peace. On the walls are four of a set of six rococo mirrored sconces (candle-holders). These are some of the few original furnishings now remaining, and all six were purchased for a total of £60 18s (£60. 90p).