@7d0b4a22 

Well, formally they are different: system building is the method of off-site prefabrication of standard components then assembled on-site.... #RAAC was one of the key components used to further reduce costs of transport (due to weight) & materials.... you can have systems building without RAAC & RAAC can be used (and has been) in other building methods. 

 @43d7c4ea Thanks, that's the impression I gained from the NAO report. I think there's much more to come out about the systems-built blocks as record keeping appears to have been patchy and proper surveying is apparently very invasive. 

 @7d0b4a22 

Yes, its a classic case of a good idea badly implemented...