Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk|Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk|Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk|Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk|Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk|Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk|Department of Statistics, University of Oxford, Oxford, UK. dilthey@well.ox.ac.uk