Classically trained at King's College, London and St John's College, Cambridge (teacher Robin Holloway), he was the Cambridge University Music Society Composer-in-Residence for 2013-14. His work for screen includes independent films The Wife and Her House Husband and Nyama (Meat), orchestration for Ralph Fiennes' The White Crow, and scores for a number of award-winning shorts. Beyond film, he has written documentary scores for The Economist, co-composed the official anthem for the International Mars Society, and had music placed in adverts by major companies like Nissan.

Commissions for the concert hall include works for the London Symphony Orchestra, the choirs of St John's and St Catharine's College, Cambridge, and the Society of Recorder Players, as well as a number of works for dance. His music has been performed in venues from the Barbican and the National Portrait Gallery to the Olympic Park.

As a session musician and writer, James has worked with artists such as Seal, Wiley, and Sneakbo, appearing on BBC Radio 1's Live Lounge. He also contributed to the Mercury Prize-nominated album Everything is Recorded alongside Richard Russell, Sampha, and Peter Gabriel.

He is a regular performer with Baluji Shrivastav OBE and his group Jazz Orient, appearing at the EFG London Jazz Festival and the Royal Albert Hall. He also performs as a solo artist.

In his role as Director, UK Classical at Wise Music Group, James represents historic publishers including Chester Music and Novello & Co. He works with a roster of world-renowned composers such as Philip Glass, Rachel Portman, Michael Nyman, Ludovico Einaudi, and Joby Talbot. He has edited over 100 publications, including King Charles III's official Coronation Order of Service, Dario Marianelli's Paddington 2 book and Olafur Arnalds' sheet music collection some kind of peace.

In addition to this, James works as a forensic musicologist and has analysed dozens of works for potential copyright infringement in a pre-court capacity.