This, the long distance human transport theory, was bolstered in 2011 by the discovery of a megalithic bluestone quarry at Craig Rhos-y-felin, near Crymych in Pembrokeshire. This is the most likely place where some of the stones were got. Another theory is that they were brought much nearer to the site as glacial erratics by the Irish Sea Glacier. This theory is not preferred, because there is no evidence of glacial deposition within southern central England.