The Royal Insurance Building, designed by architect J. Francis Doyle in 1895 to be the head office of the Royal Insurance Company, was provided with two levels of basements, but as at the Cunard building several hundred metres away, only the lowest basement level seems to have been used as a Second World War air raid shelter, and there is no surviving evidence of secondary strengthening except for the apparent building of subdividing blast walls. As one of the earliest steel framed buildings in this country the owners probably felt it was strong enough, and seem to have been more concerned with alternative escape routes.
Basement and cellar strengthening by steel and timber strutting formed a large strand of the Government’s Air Raid Precautions policy. Other city centre buildings are known to have similar basement shelters.
One problem with having shelters in basements is that, even if the basement is strong enough to withstand the building collapsing in on it, escape routes are blocked by building debris. In this case secondary escape routes were provided as an afterthought by cutting diamond shaped holes between the new basement rooms. The diamond shape seems paradoxical, as a rectangular opening with a lintel would be stronger in compression, but the shape appears to have been chosen to deal better with the complex multi-directional forces generated by bombing.
In addition, vertical escape routes are provided via pre-existing building perimeter vents (these have also been described as coal chutes or service ducts and their original function is unclear) handily signed either as “Escape” or “No Exit”, presumably to retain one in each chamber for the original purpose.