Acknowledgements

The work reported here would not have been possible without the technical support provided by colleagues from our home institutes. We thank, in particular, D.Campbell, C.Raine, I.Clark, P.Evans, S.Greenwood, H.Baughan, S.Johnson, V.Kasey, R.Knott, and M.Rankin for their contributions to the construction of the prototype RICH and its associated gas system and read-out electronics. Colleagues from the LHCb Collaboration have provided valuable advice and assistance during the beam tests at CERN, especially, R.Forty, G.McEwen, O.Ullaland and T.Ypsilantis. The silicon beam telescope was provided for us as a working system by E.Chesi and J.Seguinot. E.Nappi provided some of the aerogel samples and advised on its handling. Finally, we gratefully acknowledge the CERN PS division for their provision of the test beam and the UK Particle Physics and Astronomy Research Council for their financial support.