This work was carried out by myself and my colleagues: Iwan Williams, Carl Murray, Kevin Beurle, Sean Greaves (all at QMW) and Don Taylor and Derek Jones (RGO). It was funded by the U.K. Particle Physics and Astronomy Research Council. The JKT is operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. We wish to thank the staff of the observatory for their support and invaluable assistance.