BLACKTHORN, a chapelry in the parish of AMBROSDEN, hundred of BULLINGTON, county of OXFORD, 3 miles (S.E. byE.) from Bicester, containing 393 inhabitants. The chapel is in ruins. The Roman Akeman-street enters the county here, and proceeds over Blackthorn hill, in its course through the parish. The custom of running at the quintal, or quintain, the origin and practice of which are attributed to. the Romans, was anciently observed on the occasion of a wedding in this chapelry.