Blagdon House was built on the site of a much older manor between 1735 and 1752, for Matthew White, a Newcastle merchant and Lord Mayor, and his son, Sir Matthew White, Baronet. The architect is unknown.
The house has been altered at various dates. In 1782, the original pilasters and cornices were removed from the east front; in 1826 a large portico was built at the front door, designed by Ignatius Bonomi; and at about the same time the wing to the north by John Dobson. In 1945, the portico and various Victorian additions were removed following a fire.
The present owners are Lord and Lady Ridley, descendants of the original owner, and are arborists, having planted numerous trees of all kinds from many countries on the property. This planting program continues through the interest of Lord Ridley and also his son.