Sir Thomas Webster was a London financier, landowner and politician who acquired the Battle Abbey estate in 1721 from the 6th Viscount Montagu. The acquisition included several Sussex manors, including Agmerhurst.

The specific Agmerhurst inclusion is stated in the estate description associated with the 1721 purchase.

Research sources:
- Henry Whistler, ‘Whistler, Henry’, Epsom and Ewell History Explorer, citing Rose Fuller Whistler, The Annals of an English Family, Sussex Archaeological Collections, volume 35 (1887); The Huntington Library, Battle Abbey Archives, 1077-circa 1830; English Heritage, History of Battle Abbey and Battlefield. — https://eehe.org.uk/33503/whistler/