Unheeded warnings over crumbling concrete

Sir, The reinforced autoclaved aerated concrete (RAAC) crisis seems remarkably similar to that involving high alumina cement (HAC) 50 years ago. In June 1973 three roof beams collapsed in the Bennett Building of Leicester University, fortunately when the room was empty. In 1974 the roof of a swimming pool in Stepney collapsed, also because of HAC, and again purely by chance nobody was killed or injured. As a result over the next few years hundreds of buildings were expensively retrofitted with an internal steel skeleton, including the Physics Building in Leicester where I worked. In Europe some buildings had to be demolished. We now know, from the Grenfell Tower tragedy, that our building rules are often ambiguous and poorly enforced, but I find it surprising