Lionsheart was formed in the West Midlands in 1990, by former Grim Reaper and Onslaught vocalist Steve Grimmett, alongside twin musicians Mark and Steve Owers formerly of Fury and Touche. Lionsheart with the addition of drummer Anthony Christmas and keyboardist Graham Collett soon released a set of demos coming from the classical rock mold. In 1992 the twins quit the band two shows into the Lillian Axe British/European tour necessitating the recruitment of guitarists Nick Burr and Zakk Bajjon. The new lineup opened for Magnum on the British tour.
While Lionsheart scored success in Japan on their first album entitled Lionsheart, their follow up album titled, Pride in Tact, achieved another success, selling over 100,000 copies in Japan. Faced with a cold response from the British press, the group's reaction from British rock fans was lukewarm. In spite of this, the band garnered a successful tour in 1995 with labelmates Tyketto. Anthony Christmas was replaced with Michael O'Brien at this time.
Their third effort, Under Fire, took three years to emerge as legal battles with its record company waged on. Finally released in 1998, the album featured Grimmett and Tyketto guitarist Brooke St. James, Graham Collett and O'Brien. The sales were poor. At this time, Lionsheart folded and Grimmett founded Pride. In late 2000, Grimmett unveiled Seven Deadly Sins. Joining him on this venture was Collett, Eddie Marsh on bass and Peter Newdeck on drums.
A live recording titled Rising Sons – Live in Japan 1993 emerged in 2000 via the Zoom Club label. Finding some new momentum, Lionsheart reformed and self-financed a new studio album Abyss. Recorded at the Warehouse Studio in Oxford throughout May and June 2003. Dallas, Texas based label Metaledge Records released this album digitally in June 2004 in North America, and Italian based label Frontiers released the album to the rest of the world. Lineup changes brought Gavin Cooper to the band in May.
In late 2006 Grimmett unveiled his brand new Tewkesbury based band project, simply titled The Steve Grimmett Band, this unit involving guitarist Ian Nash, bassist Ritchie Walker and drummer Pete Newdeck. Album recordings were co-produced by Newdeck and Pink Cream 69 bassist Dennis Ward.
In July 2008 Grimmett was announced as fronting the Fargo, North Dakota Heavy Metal band Grimmstine, assembled by Methuselah and Dozer guitarist Steve Stine in union with the Sons of Poseidon rhythm section of bassist Hat and drummer Dave Johnson. The latter also has credits with Denied By Christ and Methuselah.