Nevermind the longest, what about the shortest title of a single that’s made the UK chart?
Three singles spring to mind that have hit the UK singles chart that consist of just one letter, or number:
“7” by Prince & The New Power Generation (No.27 in December 1992)
“U” by Loni Clark (No.28 in January 1994)
“X” by Xzibit (No.14 in March 2001).
The shortest title of a number one is “If” by Telly Savalas (No.1 in Feb 1975)!
Talk About Pop Music 