Which of these songs was the first to reach number one in the UK four times by four different artists?

"Unchained Melody" is a 1955 song with music by Alex North and lyrics by Hy Zaret. North used the music as a theme for the little-known prison film Unchained, hence the name. Todd Duncan sang the vocals for the film soundtrack. It has since become one of the most recorded songs of the 20th century, most notably by the Righteous Brothers. According to the song's publishing administrator, over 1,500 recordings of "Unchained Melody" have been made by more than 670 artists in multiple languages.

The first song to have reached number one four times by different artists is:

"Unchained Melody" — Jimmy Young (1955), The Righteous Brothers (1990), Robson & Jerome (1995) and Gareth Gates (2002)

The other three songs have reached number one three times by different artists:

"Spirit in the Sky" – Norman Greenbaum (1971), Doctor and the Medics (1986) and Gareth Gates and The Kumars (2003)

"You'll Never Walk Alone" — Gerry & The Pacemakers (1963), The Crowd (1985) and Robson & Jerome (1996)

"With a Little Help from My Friends" — Joe Cocker (1968), Wet Wet Wet (1988) and Sam & Mark (2004)

The achievement was equalled by: "Do They Know It's Christmas?" — Band Aid (1985), Band Aid II (1989), Band Aid 20 (2004) and Band Aid 30 (2014)