Gibraltar's first sovereignty referendum is celebrated annually on Gibraltar National Day (10 September). It is a public holiday, during which most Gibraltarians dress in their national colours of red and white. Until 2016, the tradition had been to also release 30,000 similarly coloured balloons, which represented the people of Gibraltar. However, this tradition has now been ended because of the threat that it poses to wildlife, particularly marine. The 300th anniversary of Gibraltar's capture was celebrated in 2004 on Tercentenary Day (4 August), when in recognition of and with thanks for its long association with Gibraltar, the Royal Navy was given the Freedom of the City of Gibraltar and a human chain of Gibraltarians dressed in red, white and blue, linked hands to encircle the Rock. On 4 June 2012, the Gibraltar Diamond Jubilee Flotilla, inspired by the Thames Diamond Jubilee Pageant, celebrated sixty years of the Queen's reign.