 The modules could be erected as quickly as the parts could reach the site—indeed, some sections were standing within eighteen hours of leaving the factory—and since each unit was self-supporting, workers were able to assemble much of the building section-by-section, without having to wait for other parts to be finished.Fox, Henderson and co took possession of the site in July 1850 and erected wooden hoardings which were constructed using the timber that later became the floorboards of the finished building.More than 5,000 navvies worked on the building during its construction, with up to 2,000 on site at one time during the peak building phase.