Probably a reference to the Contractor David Davies (1818-1890) of Llandinam. The 'partner' may refer to either the Chairman George Hampton Whalley, M.P., of Ruabon, or the Deputy Chairman William Lefeaux, a local mine owner.

Reference:
Gasguoine, C. P. The Story of the Cambrian: A Biography of a Railway.: (Wrexham and Oswestry, Woodall, Minshall, Thomas & Co, 1922) pp. 23-24