"Heyday" is a song by Irish-American rock singer, Mic Christopher, released in October 2000 as the title track from his first solo EP 'Heyday'.

[2] The song peaked at 11 in the Irish Charts after Heyday EP was re-released on 23 January 2004.

[3] The song gained fame in December 2003 after it appeared on the Guinness advert Quarrel, starring Michael Fassbender.

“Music is obviously an important part of advertising and particularly Guinness advertising,” “The idea to pick ‘Heyday’ was down to Nick(Kelly) who used to be the lead singer in The Fat Lady Sings and has a huge breadth of knowledge of the Irish music industry and music in general.

The second thing was that he wanted a rhythm from the start, so from the very start of the ad you have motion.” -Damian Devaney of Guinness Michael Fassbender also appears in the music video [4] The single was re-released on January 23 2004 as a result of the Guinness advert released a month earlier.