Westwood was the lead guitarist for the group and the original falsetto singer on the band’s only number one, Silence Is Golden.

The band mostly covered rock and roll songs of the 1950s, and appeared on shows such as Ready Steady Go!, Top of the Pops, and the NME poll winners concerts in 1964.

After Poole's departure in 1966, the band achieved further success as a four-piece with 13 top 40 hits on the UK Singles Chart between 1967 and 1971 including "Here Comes My Baby", "Even the Bad Times Are Good", "(Call Me) Number One", "Me and My Life" and their most successful single, "Silence Is Golden" (1967).

[8] Westwood played bass guitar on "Sweet Illusion", a 1973 a minor hit penned and recorded by Junior Campbell of Marmalade.

Jimmy Page of the Yardbirds and Led Zeppelin once noted Westwood as “one of the world’s best guitarists.”[3] In December 2015, it was reported that Westwood and Tremeloes member Chip Hawkes would stand trial for the April 1968 assault of a then-fifteen-year-old girl[11] at a hotel in Chester.

[12] In December 2015, while leaving Chester Crown Court, both he and Hawkes were assaulted by an intoxicated photographer, who had to be restrained by their barrister.