School of Computing Sciences, University of East Anglia, Norwich, NR4 7TJ, UK. martin.lott@uea.ac.uk|School of Computing Sciences, University of East Anglia, Norwich, NR4 7TJ, UK. martin.lott@uea.ac.uk|School of Computing Sciences, University of East Anglia, Norwich, NR4 7TJ, UK. martin.lott@uea.ac.uk|School of Computing Sciences, University of East Anglia, Norwich, NR4 7TJ, UK. martin.lott@uea.ac.uk