A British guitarist formerly in the electric folk band Steeleye Span from 1972 to 1977 and again from 1980 to 2002.

Born in London, his mother was a music teacher.

He became a member of Steeleye Span in 1972, after being introduced by fiddler Peter Knight, and first appeared on the group's fourth album, Below the Salt. Despite taking lead vocals on many songs, Johnson was something of a background member. He left Steeleye temporarily in 1977 to work on a concept album called The King of Elfland's Daughter with Knight, but returned in 1980 to record Sails of Silver.

After Tim Hart's departure from the band in 1980, Johnson became the sole guitarist and a more prominent member, taking on a central role for the albums Back in Line (1986) and Tempted and Tried (1989).

Johnson left Steeleye Span in 2000 due to health reasons, but returned in 2002 to record Present - The Very Best of Steeleye Span. However, his remaining health issues prevented him from touring, so he was replaced by Ken Nicol.