James is a composer and writer whose work encompasses choral and orchestral works, music for film and theatre, and a whole range of smaller works and arrangements. His music has been commissioned for many ensembles and performers, including the choir of Westminster Abbey, Graham Johnson with The Songmakers’ Almanac at the Wigmore Hall, Guy Bovet, James Bowman, the Beauregard Youth Choir and the Bromley Boy Singers. He collaborated on the song cycle Voices of London for Song in the City and his work has been performed by English Voices, Vivamus and the choirs of St Paul’s Cathedral and Trinity College Cambridge, with recordings by the choirs of Girton and Selwyn and the chapel choir of Bedford school. Recent commissions include his Concerto For Orchestra, premiered in 2024 by the Bridgewater Sinfonia.

Musical theatre writing includes Infants, MusicalTalk's pick of the 2011 Edinburgh Fringe Miracles at Short Notice and the award-winning total Fringe sell-out show Tony Blair the Musical. He wrote and directed the music for Io Theatre Company's actor-musician adaptations Dickens’ Ghosts, A Christmas Carol and The Snow Spider, their realisation of J. M. Barrie’s A Well Remembered Voice, and their forthcoming drama cabaret and The Confessions of Fanny Cradock. Other productions, as both a composer and musical director, include The Snow Queen and Peter Pan: the Revenge of Captain Hook (Rolling Stock Theatre Company), The Borrowers (Dreamshed Theatre), and a setting of new words by Andrew Motion for Bush Theatre’s Sixty-Six Books at Westminster Abbey. 

He studied composition with Robin Holloway and was the composer-in-residence at Bedford School between 2008 and 2011.