Glen started playing harmonica after seeing Muddy Waters, and the ‘American Folk-Blues Festivals’ which visited London in the late 1960s and early 1970s. His early influences being Little Walter, Sonny Boy Williamson, and Junior Wells. Early bands he was involved with were Crowjane Bluesband, The Radical Sheiks and Brothers Grimm, before going on to join Nine Below Zero (1991–1995), and The Yardbirds(1996–2003 and 2008–2009).
Glen has played on over 50 albums and recorded/performed with: Alannah Myles, Jeff Beck, Steve Vai, Slash, (on the Yardbirds’ album Birdland) John Mayall, Steve Lukather, Skunk Baxter, Lee ‘Scratch’ Perry, Horace Andy, Junior Delgado, Bernie Marsden, Paul Jones, Papa George, Geoff Everett, Gary Fletcher, Gordon Smith, Micky Moody, he has recorded eight albums with Little Axe. In addition he appeared alongside Alan Barnes, Jim Mullen and Roger Cotton on the With Friends Like These album for the Barcodes, which also included Zoot Money. He played with Peter Green, Mick Taylor and Hubert Sumlin at the Long Beach Blues Festival.
He recorded the album On The Road Again with Dr. Feelgood. Other collaborators include Art Themen, Pee Wee Ellis, Dub Syndicate, Paul Cox, Alan Barnes, Little Axe and Gypie Mayo. Glen has played at Montreux, Brecon Jazz Festival and Nice Jazz Festivals, Hollywood House of Blues, the Hilton, Las Vegas, Sporting Lisbon Stadium, Wembley Arena, Ronnie Scott’s Club and The Royal Albert Hall, as well as various television and radio performances.
Soundcheck magazine referred to Glen as “one of the finest blues harp players and slide guitarists of his generation,” and also received praise from Net Rhythms for his harmonica playing.
Glen’s original music was used on the soundtrack of the BB King Biopic “Life of Riley”