Most UK singles to debut at No.1

The most singles to debut at No.1 in the UK chart by one band is 12, by Westlife (Ireland), between 1 May 1999 and 22 November 2003. The singles were: 'Swear It Again' (1 May 1999), 'If I Let You Go' (21 August 1999), 'Flying Without Wings' (30 October 1999), 'I Have A Dream/Seasons in the Sun' (25 December 1999), 'Fool Again' (2 April 2000), and 'Against All Odds' (24 September 2000), 'My Love' (11 November 2000), 'Uptown Girl' (17 March 2001, 'Queen Of My Heart' (17 November 2001), 'World Of Our Own' (2 March 2002), 'Unbreakable' (16 November 2002), and 'Mandy' (22 November 2003)