Phase 3b: Shell and Core Construction of a New Four-Storey over Two-Storey Basement Structure: Works include the construction of a new weather tight four-storey over two storey basement rear extension (716 m²) to the Protected Structure including lift and stair cores, external finishes, glazing, primary and secondary steel and masonry works. The protected structure and new extension will be linked by an atrium space with glazed roof and connecting walkways, which will be constructed as part of this phase. Restoration works will also be carried out to the basement walls and floor of the Protected Structure including a new floor slab, drainage and waterproofing detailing with continuity into the extension. M and E service installations will not be included in this phase.