TL:DR – Knott’s Flats in Tynemouth were built in the 1930s with air-raid shelters and others features that had a coming war in mind.
The “Sir James Knott Memorial Flats” in Tynemouth, commonly known as Knott’s Flats (although they have also been known locally as Colditz), were built when war clouds were gathering over Europe in the 1930s, ironically enough.
They had special design features meant to protect the occupants from putative air-raids, probably the first residential building to be designed for such an eventuality. They had lots of fire-resistant materials (asbestos, presumably) and huge cellars constructed as in-house air-raid shelters.
They were completed in 1938 and are still home to many people today. More information about the heritage of Knott’s Flats (which at one time had the biggest clock in the North East) can be found here. What they lacked were anti-aircraft gun emplacements…oddly.