Philip Kenneth Collen (born 8 December 1957)[1] is an English musician who is best known as the co-lead guitarist for the rock band Def Leppard.

[2] Before joining Def Leppard, Collen had performed with a number of bands in the burgeoning British glam metal scene.

[4] During his tenure with Girl, Collen's career began rising, spurred by the relative success of the albums Sheer Greed and Wasted Youth, which allowed him the opportunity to play at more significant venues.

[6] In an interview, Collen revealed that he was approached by Steve Harris to join Iron Maiden replacing guitarist Dennis Stratton.

[9] He and fellow guitarist Clark quickly bonded, becoming close friends and leading to the trademark dual-guitar sound of Def Leppard.

According to Collen, he had begun suffering from blackouts due to alcohol and stopped drinking when he realized that his addiction was starting to dominate his life.

[11] After Clark died, Collen was faced with the challenge of dealing with the loss of a friend and bandmate as well as the burden and responsibility of the Adrenalize recordings.

Due to the aftermath of Clark's death, as well as the issues with the recording of Adrenalize, Collen seriously considered leaving Def Leppard.

[12] Clark would ultimately be replaced as the band's co-lead guitarist by Vivian Campbell, formerly of Dio and Whitesnake, shortly before the Adrenalize tour.

The hiring of Campbell relieved Collen of some of the pressures of the "overkill" production style of Def Leppard, as well as the challenge of reproducing Clark's guitar parts for live shows.

[10][better source needed] Collen has been involved in several side projects over his career, most notably the band Man Raze, formed as a joint collaboration with former Girl bandmate Simon Laffy as bassist and drummer Paul Cook from the Sex Pistols.

He and Elliott also joined with Trevor Bolder and Mick "Woody" Woodmansey from Spiders from Mars and keyboardist Dick Decent to form the band Cybernauts.

[17] In 2010, Collen recorded the song "Hard Times Celebrate" with rapper Bazaar Royale, featured on the album "The Ride.

"[18] Collen formed a blues project by the name of Delta Deep with vocalist Debbi Blackwell Cook of the 1980s group The Jammers, which released an eponymous debut album in 2015.