Norfolk County Hall was built in Norwich in 1966 and in the lower basement (Rooms B38 to B47) it housed the County Emergency Headquarters.
From Norfolk Heritage Explorer (57971):
The building was officially opened by Her Majesty Queen Elizabeth II on 24th May 1968, during a visit to the city. The entire building cost around £2.5 million to construct and was at the forefront of modern sixties design both inside and out. Uren’s distinctive design drew much attention at the time - the building’s size and appearance were the subject of much discussion. The keynote design was intended “to combine civic dignity with simplicity”. Alongside the council chambers and new administrative departments, the Norfolk Police had technologically-advanced offices within the building, alongside a War Room and Forensics Department (S3).
In the lower basement (Rooms B38-47) there is an area which was designed as and still operates as a Local Authority Emergency Headquarters. Due to refurbishments there is little of obvious Cold War vintage, apart from the entrance doors and adjacent ventilation valves (one door of two in situ). There are also some probably 1960s heating and ventilation ducts, cabling etc, BBC and Raynet broadcasting stations (1980s, and the current equipment probably not original), and two small key control boxes marked “BOMB ALERT” (blue) and “ALL CLEAR” (green). (D Gurney HES, 2013)
In 2019 the lower basement was completely stripped and refurbished with no trace of it remaining.