Erm. It's an air-road shelter. It was built in WW2. It's made of reinforced concrete. It hasn't been demo'ed yet! What's more to know? Oh...this:
"Adjacent Abbey Circus houses a small green band notable for its WW2 air raid shelter, which is still in existence today. Earmarked for demolition in 1979 as the Cold War drew to a close, the 67 ft shelter (B34TYB) was mothballed but recently added to a list of possible shelters to be re-commissioned in light of recent global unrest."