[singing] Hi ho, hi ho...
but seriously... could be postmortem (because of the burial, weight of the soil, moisture, etc), or could have been due to ancestry (Sarmatian? Some other group off the steppe? The Romans eventually defeated the Sarmatians, sent the men into Auxiliary duty in far-flung parts of the Empire, including Britain, sold off the women and children), or diet.
It could be a relative of mine, us Highland folk have short legs and long torsos and, yes, a big head! but not a close relative due to lack of body hair that i am all but positive would have survived that long!