Turner was replaced by bassist and vocalist John Wetton, formerly of Family, King Crimson, Roxy Music, Uriah Heep and UK. Number the Brave was released in April 1981 and featured Wetton's lead vocals on just one song, although during album sessions he had offered songs such as "Here Comes the Feeling" that would eventually sell millions when released on Asia's 1982 debut album. Wetton did not continue with Wishbone Ash beyond the album sessions and rejoined Asia. Wetton was replaced on the Number the Brave tour by the former Uriah Heep bassist Trevor Bolder. Also joining the band was female backing vocalist, Claire Hamill, who had sung on both the Just Testing and Number the Brave albums. In 1982, after Hamill's departure, the band experimented with heavy metal on the Twin Barrels Burning album. It became the highest charting Wishbone Ash album in years (UK #22). Bolder left the group to rejoin Uriah Heep in 1983, to be replaced by bassist/vocalist Mervyn Spence (ex-Trapeze). The group continued with a heavy metal side on 1985's Raw to the Bone, which became the first Wishbone Ash album not to make the charts. Not long after, Wisefield left after serving as guitarist in the band for eleven years, going on to a varied career that would include work with Tina Turner, Joe Cocker, Roger Chapman, Jeff Wayne and the Queen musical We Will Rock You. He was replaced by Jamie Crompton, who in turn was succeeded briefly by Phil Palmer. Early in 1986, Mervyn Spence quit as well, to be replaced by ex-Kinks bassist Andy Pyle.

Answer this question "Why did Wisefield leave?" by extracting the answer from the text above.
going on to a varied career that would include work with Tina Turner, Joe Cocker, Roger Chapman,