Air Raid Shelter Query

Is this an air raid shelter in Kate's garden?
Image courtesy of Kate Roffey


I’ve recently moved to Leamington Spa and have, from what I can tell, an air warden’s shelter in my back garden.

Is this a common thing? And if so do I own this or is this something the council owns? I’d appreciate any information you might be able to provide about this shelter, or a point in the right direction.