The following year he replaced Denny Laine as lead singer of the Moody Blues. The band’s first album after Justin joined, the innovative and iconic Days of Future Passed, has sold over two million copies. The Moody Blues’ total album sales stand at well over 60 million, thanks mainly to a run of eight top ten studio albums from 1968 to 1981, from In Search of the Lost Chord through to Long Distance Voyager.

From 1967 to 1974 Justin was the Moody Blues’ main singer and most prolific songwriter, writing 20 of the group’s 27 singles in that period, including such classics as ‘Nights in White Satin’, ‘Question’, ‘I Know You’re Out There Somewhere’ and ‘Tuesday Afternoon’.

In 1975 Justin and fellow Moody Blue John Lodge collaborated on the Top Five album Blue Jays and the non-album single ‘Blue Guitar’, which became a hit. Three years later Justin had another hit with ‘Forever Autumn’ from Jeff Wayne’s War of the Worlds. 

Justin never forgot his roots and the early influence of Buddy Holly. He recorded a version of Buddy’s ‘Learning the Game’, which was included on the CD re-release of his debut solo album, Songwriter. In August 1983, when he appeared on the Mike Read-hosted Radio One Roadshow at St Ives, he and Mike played a Buddy Holly song live on air and on stage.

In 2000 Justin was awarded the Golden Note by the American Society of Songwriters, Composers and Publishers and in 2004 he was awarded the Gold Badge by the British Academy of Songwriters, Composers and Authors for Lifetime Achievement. He is a member of the Society of Distinguished Songwriters and in 2018 he was inducted into the Rock and Roll Hall of Fame as a member of the Moody Blues. In 2022 he was awarded the OBE for services to the music industry. The year 2024 saw Justin receive his Buddy Holly guitar from the Buddy Holly Educational Foundation, just prior to undertaking another lengthy tour. Buddy would have been proud.