Berte Thomas appeared in London as Caspar in Once Upon a Time at the Haymarket Theatre in March 1894 as part of Herbert Beerbohm Tree's company with which he worked as a supporting player for several years, touring North America with them in 1895. From the early 1890s and during his time at Sarah Thorne's academy he had written plays. In June 1893 he took the title role in his own melodrama, Joe the Miner, produced at Margate, about a miner drawn into an illegal plot to ruin a neighbouring mine. In A Little Brown Branch a woman gives up the man she loves to her younger sister; Thomas played the role of the man they both love. Thomas's next play, My Son, about a wife who discovers her husband and then her son are criminals and shoots the latter was respectfully received, with Frances Ivor's performance in the leading role of the mother being much praised by James Agate.