Produced by Beatles super-producer George Martin, Fourmost scored several U.K. chart successes including the John Lennon-penned tune "Hello Little Girl" (No. 9), Lennon and McCartney's "I'm in Love" (No. 17), and "A Little Loving" (1964, No. 6). In 1965 the group released their only album, First and Fourmost, a collection of country, comedy, and rock 'n' roll songs. Fourmost were part of a long-running variety show at the London Palladium and appeared in two 1965 British films, Pop Gear and Ferry Cross the Mersey. Ultimately giving up trying to make the charts, Fourmost settled into the well-paying world of cabaret. The band fragmented in 1978 with several members forming Clouds. O'Hara continued as Fourmost with three local musicians, but sold them the name after a few years when he left to set up a used car business.
On June 27, 1999, the 58-year-old former musician was found hanged at his home in Smithdown Road in the Wavetree area of Liverpool. Terence O'Hara, the dead man's brother, told an inquest that he found the guitarist in his underpants and shirt hanging from a ligature in an attic stairwell. In the absence of a suicide note, authorities estimated that O'Hara had been in that position for a number of days. According to his brother, O'Hara had financial worries.