In the early 1970s, Slesser joined Beckett, replacing original singer Rob Turner, who had been killed in a car accident.
[4] In 1981 after the departure of Paul Di'Anno, Slesser unsuccessfully auditioned for the lead vocal in Iron Maiden (as mentioned by Steve Harris on the Iron Maiden The Early Days DVD,[citation needed] In 1983, Slesser joined the band Charlie as lead vocalist.
Slesser was featured on the band's US hit single "It's Inevitable", and the related album.
[5] In 1984, Slesser toured Europe, Japan as an offstage backing vocalist with the Michael Schenker Group.
For two years, he was the lead singer of Freeway, a British Free tribute band.