It has recently been suggested that the work of Thomas Brassey, a major nineteenth century contractor, is worthy of further study. Unfortunately he instructed that his papers should be destroyed upon his death. However court papers were published concerning his claim against his client for compensation for additional costs as the result of adverse ground conditions during the construction of the Hauenstein tunnel in Switzerland and his client’s counterclaim for the effects of late completion. These documents, along with a descriptive account written by the client’s former section engineers, enable a reconstruction of events placed in their geological and contractual background. The developing breakdown of the relationship between contractor and client is apparent. The content of the claim, counterclaim and court decision are summarised. Aspects of the character of Brassey revealed are found to differ from the descriptions provided by his nineteeth century biographer.