Nuclear free zones were an early 80s political phenomenon that swept Labour run local councils, student unions and other bodies. They were always derided by the Tories as a vainglorious gesture by grandstanding politicians. However, they captured a widespread anxiety about the threat of nuclear war that was very pervasive in the late 70s and early 80s. The turnout on CND demos surged massively at the turn of the decade and I remember being on one monster march to Hyde Park in 1981.
Here’s an announcement that Merseyside County Council (later abolished by Thatcher along with the GLC and other authorities that were nearly all Labour run) was going to declare itself a nuclear free zone.