It's possibly because there are umpteen versions available, from performances by various orchestras (BBC Concert Orchestra to Philomusica of Edinburgh), through

It's possibly because there are umpteen versions available, from performances by various orchestras (BBC Concert Orchestra to Philomusica of Edinburgh), through versions with added lyrics (one by Bernard Loughrey, others including a male voice choir and one by Binge himself and the Wimbledon Girl Singers), to people who captured it from broadcasts; as well as Wikipedia articles that are easily discoverable. The UK Theme also has several broadcast versions, alone, of differing lengths. * https://en.wikipedia.org/wiki/Sailing_By https://en.wikipedia.org/wiki/Sailing_By * https://www.youtube.com/watch?v=Pr-T3vXbj8c https://www.youtube.com/watch?v=Pr-T3vXbj8c * https://www.youtube.com/watch?v=p6vDtPOhDqA https://www.youtube.com/watch?v=p6vDtPOhDqA * https://www.youtube.com/watch?v=vSvf_wMfzLE https://www.youtube.com/watch?v=vSvf_wMfzLE * https://www.youtube.com/watch?v=pFfftvIVVyo https://www.youtube.com/watch?v=pFfftvIVVyo * https://www.youtube.com/watch?v=CP_4w6GOQS0 https://www.youtube.com/watch?v=CP_4w6GOQS0 * https://www.youtube.com/watch?v=QlPSuqXlS4I https://www.youtube.com/watch?v=QlPSuqXlS4I * https://en.wikipedia.org/wiki/Radio_4_UK_Theme https://en.wikipedia.org/wiki/Radio_4_UK_Theme