Following the 1066 country trail all day skirting by Herstmonceux Castle and ending by Pevensey Castle. Pub stop en route. At the end there's a chance for a well earned dip in Pevensey Bay. Pub at the end.
Please bring a packed lunch.
Travel: Take 9:15 London Charing Cross (9:24 London Bridge), arr. Battle 10:33.
Buy a return to Pevensey and Westham (I would advise to return to London via Hastings and thereby keep to the Southeastern train network as your ticket may not be valid on Southern trains via Eastbourne all the way back to London).