Thomas began his career as an accountant with the entrepreneur Peter Jones before joining MacCorkindale International to work with some of the biggest names in film, television and music. In 2004 he was appointed managing partner of their London and Los Angeles offices while consulting to their offices in Nice, Cape Town and Sydney.  It was during this time that Thomas realised the need to adapt the US business management model to the UK entertainment industry. Thomas St John LLP was formed in 2007 and quickly established itself as a leader in the sector.

Thomas caters exclusively to creative talent and his firm has seen exponential growth as a result. He represents a broad range of clients from established artists, songwriters and producers through to new and unsigned acts. His clients include Deadmau5, Sophie Ellis-Bextor, Sacha Skarbek and Hurts but to name a few.