Digby Fairweather has been a full-time jazz musician since 1 January 1977, and he worked part-time for seven years before that with several local jazz bands in Essex and London. He recorded his first album in 1975 with Alex Welsh's band, as deputy for Welsh. When turning professional, Fairweather helped found the Keith NicholsMidnite Follies Orchestra. From 1978 he recorded solo albums, and joined a quartet known as Velvet, with guitarists Denny Wright and Ike Isaacs plus bassist Len Skeat. Before becoming a professional musician he was a librarian and has retained a strong interest in jazz bibliography and archiving.
In 1979, Fairweather became co-director of the non-profit Jazz College along with pianist Stan Barker. He also joined the Pizza Express All Stars. From 1983 he began leading bands of his own and helped to revitalise the Kettners Five, co-led with veteran double-bassist Tiny Winters. In 1983, Fairweather and Winters collaborated in a touring tribute to Nat Gonella, and they worked on various projects together over the next decade. Fairweather's musical style has been influenced by a number of artists, particularly Louis Armstrong, Ruby Braff, Billy Butterfield, Bobby Hackett, Red Nichols and Gonella. Digby’s Half Dozen was formed in 1995 and they toured and recorded with singer George Melly in the later years of his career (2003–07). Thereafter, Fairweather's band toured with former Manfred Mann lead singer Paul Jones in their presentation titled 'Rocking in Rhythm' (2007–present). Apart from his playing and bandleading, Fairweather has long pursued a parallel career as a broadcaster and writer on jazz.
From 1985 to 1988 he worked and recorded with Brian Priestley's Special Septet and Tony Milliner's Mingus Music, and he wrote the book How to Play Trumpet. By 1990 he had embarked on a dual vocation as broadcaster for BFBS, BBC World Service, Jazz FM (1991–92) and BBC Radios 2/3 (1992–98), including occasionally deputising for Humphrey Lyttelton on the show Best of Jazz and successively presenting Jazz Parade and Jazz Notes. In 1987 Fairweather founded the Association of British Jazz Musicians and the National Jazz Archive. That same year he formed the Jazz Superkings (with Dave Shepherd, Brian Lemon, Allan Ganley, et al). Fairweather also helped bring jazz musicians into the British Musicians' Union by proposing, then founding, its Jazz Section in 1992. In 1994 (with trombonist Pete Strange) he co-founded The Great British Jazz Band and continues to teach and do solo work. Following the death of Humphrey Lyttelton, he was invited to succeed Lyttelton as the Patron of the Birmingham International Jazz Festival. In 2013 he continues to lead his Half Dozen (winners of the Best Small Group category at the 2012 British Jazz Awards) and to perform as a soloist.