to house the returning civilians. A programme to build housing projects was implemented, though progress was slow due to shortages of building materials. By 1969, over 2,500 flats had either been built or were under construction. In the war's aftermath, Gibraltar took decisive steps towards implementing civilian self-governance over most issues of public policy. The Association for the Advancement of Civil Rights (AACR), led by Gibraltarian lawyer Joshua Hassan, won all of the seats in the first post-war City Council elections in 1945. Women were given the right to vote in 1947, and in 1950 a Legislative Council was established. A two-party system had emerged by 1955 with the creation of the Commonwealth Party as a rival to the AACR. That same year Hassan became the first Mayor of Gibraltar. The Governor still retained overall authority and could overrule the Legislative Council. This inevitably caused tension and controversy if the Governor and Legislative Council disagreed, but in 1964 the British Government agreed to confine the powers of the Governor to matters of defence, security and foreign relations. A new constitution was decided on in 1968 and promulgated in 1969, merging the City Council and Legislative Council into a single House of Assembly (known as the Gibraltar Parliament since 2006) with 15 elected members, two non-elected officials and a speaker. The old title of "Colony of Gibraltar" was dropped and the territory was renamed as the City of Gibraltar. Gibraltar's post-war relationship with Spain was marred by an intensification of the long-running dispute over the territory's sovereignty. Although Spain had not attempted to use military force to regain Gibraltar since 1783, the question of sovereignty was still present. Disputes over smuggling and the sea frontier between Gibraltar and Spain had repeatedly caused diplomatic tensions during the 19th century. The neutral zone between Spain and Gibraltar had also been a cause of disputes during the 19th and 20th centuries. This originally had been an undemarcated strip of sand on the isthmus between the British and Spanish lines of fortifications, about wide – the distance of a cannon shot in 1704. Over the years, however, Britain took control of most of the neutral zone, much of which is now occupied by Gibraltar's airport. This expansion provoked repeated protests from Spain. Spain's push to regain sovereignty over Gibraltar was fuelled by the decolonisation agenda of the United Nations, which had been initiated in 1946.