The Museum's Arch Five is not a public-access area.
The museum's Fifth Arch area, with its own separate door alongside the upper fire escape and wheelchair entrance, is not used for display or for storage of important pieces, and is not currently integrated with the rest of the museum.
This arch is occasionally used for storage of large awkward materials (such as building materials) and for occasional larger-scale construction work.
The space had its "legacy" internal structures removed in around 2014-2015, and after some serious cleaning is now undergoing long-term dehumidification to try to dry out its rather damp brickwork, with industrial dehumidifiers installed and running "around the clock", 24/7. Since these Victorian structures have arched brick walls that are around three feet thick at their thinnest points, drying out this arch to make it suitable for general use is likely to take some time.
However, this improvement work can't be anything but good for the rest of the museum, as it means that our neighbouring arch is less likely to be the cause of any sideways water seepage problems into the structure of our main display arches, and having a "dry arch" alongside will also make it easier to spot any potential new problems overhead.
The floor level within this arch is significantly higher than that of Arch Four, so while having it as an additional display space would be wonderful, it would not currently seem to be practical - it'd require cutting at least one new passageway through the wall of a listed building, and cutting down into the existing "Arch Five" floor to create a wheelchair-accessable ramp to the Arch Four floor level, and making the Arch Five doorway the new entrance for wheelchair access.
In any case, the humidity levels in Arch Five are not yet suitable for storing historically-important museum artefacts. Our current default plan is to eventually use the rear of this space as an extension to or replacement for the current Construction workshop.