The paper describes the theoretical modelling and experimental validation of a novel design of ocean wave energy converter which is comprised of a floating, moored, spherical hull containing a mechanical pendulum arrangement from which power is taken when excited by incident waves. Experimental results are shown to compare favourably with those predicted by the theory. An explicit expression is derived for the capture width of the proposed device in terms of physical and hydrodynamic parameters. This exposes the multiple resonant characteristics of the device which enable it to operate effectively over a broad range of wave periods. The subsequent efficient computations allows a numerical optimisation of the design to be performed over a large space of device parameters and model sea spectrum. The work is focussed towards producing reliable estimates for the power capacity of different sized devices deployed at the EMEC site in Scotland. Predictions compare favourably with existing wave energy converter concepts. (C) 2017 Elsevier Ltd. All rights reserved.