English heavy-metal band formed in Stourbridge in 1976 by guitarist Brian Tatler and drummer Duncan Scott, and one of the first bands classed as NWOBHM, or New Wave of British Heavy Metal. They are also perhaps best known as one of the main influences on Metallica (and to some extent Megadeth).

Long-time vocalist Sean Harris joined shortly after the band's formation. They band released their first album in 1980 after a series of singles and independent demos, and continued releasing material and touring until their first breakup in 1985.

The band reformed again in 1991, and released the Death & Progress album. However, the band was close to breaking up just after the record's release and eventually did in 1994, not reforming again until 2000. They released the Acoustic Cuts EP but again broke up (due to Harris' problems with the rest of the band) in 2004.

In 2004 the band brought in replacement singer Nick Tart, and recorded their first full album in years entitled All Will Be Revealed, released in 2005. They toured with Megadeth throughout the year, also appearing at an anniversary concert for the NWOBHM scene at the London Astoria. In 2006 they also released both a live album and their first DVD, and started writing their 2nd album with Nick Tart. What's In Your Head? was released in 2007 and the band supported the album on tour with Thin Lizzy across Europe.