Statistical Laboratory, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, UK. C.Spyrou@statslab.cam.ac.uk|Statistical Laboratory, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, UK. C.Spyrou@statslab.cam.ac.uk|Statistical Laboratory, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, UK. C.Spyrou@statslab.cam.ac.uk|Statistical Laboratory, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, UK. C.Spyrou@statslab.cam.ac.uk