Seaton Delaval is a village in Northumberland, England, with a population of 4,371.Office for National Statistics : Census 2001 : Key Statistics : Seaton Delaval Ward Retrieved 22 July 2010 It is the largest of the five villages in Seaton Valley and is the site of Seaton Delaval Hall, the masterpiece completed by Sir John Vanbrugh in 1727.