Liverpool and Birkenhead were obvious bombing targets in World War II due to their docks and associated industries which included ship-building. In early 1941 permission was given for the excavation of large, deep-level air-raid shelters in Tranmere. These were to extend to an immense 6,000 occupants - 4,500 in bunks and the rest seated.
Built to a grid system, the shelters were in use from later 1941, even though they had not been completed or fitted out. In 1942 the fit-out was completed, with three entrances in former quarries, ventilation shafts, toilets and first aid posts in pace. The budget of £119,000 was exceeded by about £10,000.
The complex was sealed in 1988 after a number of incidents in which local children became lost and had to be rescued. Access was briefly restored in 2008 during building work but they are once again sealed.
