We present a new nonlinear control law to stabilise the ball and beam system at a desired operating point. The control law is based on the interconnection and damping assignment-passivity-based control (IDA-PBC) methodology developed in Ortega, Spong, Gomez-Estern, and Blankenstien (Ortega, R., Spong, M., Gomez-Estern, F., and Blankenstien, G. (2002), 'Stabilization of Underactuated Mechanical Systems via Interconnection and Damping Assignment', IEEE Transactions on Automatic Control, 47, 1218-1233) that guarantees stability in the sense of Lyapunov. We present a novel proof of the asymptotic stability of the desired operating point. The validity of the proposed control law is demonstrated through the experimental results.