Seaton Sluice Harbour sits at the mouth of the Seaton Burn on the Northumberland coast, midway between Whitley Bay and Blyth.

What began as a natural rill was transformed in the late 17th century when Sir Ralph Delaval raised stone walls, built piers, and installed sluice gates designed to use tidal surges to scour silt from the channel entrance.

Further improvements came between 1761 and 1764, when John and Thomas Delaval cut a new channel through the cliffs to give ships better access to the old harbour.

The port subsequently flourished as a hub for coal, salt, and glass exports — in 1777 alone it handled around 80,000 tons of coal, 300 tons of salt, and 1. 75 million glass bottles.

Two entrances served the harbour: the original northern entrance was used in stormy weather, while the new cut to the south was favoured in calmer conditions, with pilots signalling arriving ships by flag or, at night, a lamp of burning coal.