This was London, not Birmingham which does not have an underground rail system. Outside London — and within it for that matter — people had air raid shelters in their back yards; usually corrugated steel structures partially buried. Or they had steel tables they gathered under inside their houses to protect them from falling brickwork.
Thanks for an interesting and insightful article. The experience of war, in Britain and Europe, was so much different from that of the USA and it is welcome to see someone providing these insights.