Snippets from Trivia Mick....
Before Lord Delaval cut a secondary channel ( the "sluice"), from the River Seaton ( or the Seaton Burn ) to the sea, to help stop the little harbour clogging up with sand and mud, the place was called Hartley Haven ( sounds much better ? ).
The Delavals needed a better and safer harbour to export their glassware made in their adjacent glassworks, and their coal, thus avoiding paying big bucks to the nearby port of Blyth
Hartley Haven/Seaton Sluice lay in the "township" of Hartley, which also included community of Hartley.
Hartley was one the eight townships of the Parish of Earsdon.
When the Delavals later sunk a new coal pit, in 1830, in a green field site, just to the west, a touch north of Seaton Delaval village which lay within the "township" of Seaton Delaval ( another of Earsdon Parish townships), it was named New Hartley Colliery ( the Hester Pit)
Then the original community of Hartley attracted the name of old Hartley, to distinguish it from New Hartley.
The view from the headland(s) at Seaton Sluice is good, but lacking somewhat now that the backdrop of Blyth/Cambois power station chimneys has been removed. LOL.
The Waterford Arms there was/is renowned for serving up a nice piece of haddock etc.
Michael Dixon