A single is a type of music release defined by the British Official Charts Company (OCC) as having no more than four tracks and not lasting longer than 25 minutes. On 31 May 2011, a retrospective record chart was broadcast on BBC Radio 2 that listed the 60 biggest-selling singles in the United Kingdom during the 1960s. The programme, entitled The Top 60 Best Selling Records of the 60s, was hosted by British DJ Tony Blackburn. The chart was compiled by the OCC, and was based on sales of singles from 1 January 1960 to 31 December 1969.