This paper presents the first practical demonstration of a recently developed theory of balance control that aims to achieve high performance in the sense of allowing a robot to make large, fast movements while maintaining its balance on a narrow support. This theory includes a simple method of leaning in anticipation of future motion commands, which is largely responsible for the high performance. The experiments reported here use a robot acting as a reaction wheel pendulum, and they test only the 2-D version of the theory. The results show that the balance controller's performance in practice closely resembles its theoretical performance. This paper also presents a simple yet accurate balance offset observer that measures the difference between true and estimated balanced configurations.