This is an English surname. It originates apparently from a place called Hadlington of which there does not appear to be any surviving records. This strongly suggests that either over the centuries the surname or the place name has changed to something else, or that the former place is one of the known three thousand and more that have completely disappeared form the maps and gazetters of Britiain in the last three hundred years. The only surviving places which would seem to bear any resemblance to this surname are Hadlingham, a diminished village in Suffolk and Hoddington, a village in Hampshire, which has been variously recorded over the centuries as Hodingetuna and even in the famous Domesday Book of 1086 as Odingtone. The name means 'The place of the Hod tribe', whilst Hadlingham would see to translate as the farm of the Headda people. We cannot find any proof that this place has anything to do with the Hadlington surname anymore than Hoddington, so the mystery remains. Examples of the surname recording in the surviving church registers of Greater London include Edward Hadling who was a witness at St Mary Whitechapel on July 25th 1624, and Mary Hadlington who married John Cooper at St Georges Chapel, Hanover Square, Westminster, on July 9th 1810.