Archives of the Earls of Westmorland and the Mildmay family with estates in Apethorpe, Wadenhoe, Wood Newton, Tansor, Nassington, Yarwell, Cotterstock, Glapthorn and Oundle, Woodstone, Stanground and Farcet (Huntingdonshire), Medmenham (Buckinghamshire), Tudeley, Hale and Hadlow (Kent), Bicknacre (Essex), Woodrow and Seend (Wiltshire) and Sharlston (Yorkshire).
Oundle manorial accounts 1471-1511. Yarwell inclosure agreement 1577. Estate rentals and accounts from 16thC. Fine late 16th/early 17thC. household accounts and commonplace books. 19thC. household accounts and rentals. Inventories of 1629 (1st Earl and Ldy. Despencer), 1691 (3rd Earl), 1705, 1774 and 1842. Largely uncatalogued estate papers, early 18thC. and 1760s. including papers on Rockingham Forest, the Nene Navigation, coal mining, 18thC.
Papers of 6th Earl as Lord Warden of the Cinque Ports, early 18thC., and of the 11th Earl at Florence 1830s, 19thC. family correspondence including letters from the Crimea 1854-1855 and from Grenville Murray, 19thC. journalist.
Papers of Sir Walter Mildmay as Under Treasurer of England, late 16thC. Lady Mildmay's 'Advice to her children'. Papers on claims to the Barony of Abergavenny, late 16thC-18thC. 17th/18thC. papers on Emanuel College, Cambridge. Papers on the Lyme Regis election 1781. Papers of John Scrope as Secretary to the Treasury, early 18thC. Household accounts of Edward, Duke of York 1409-1410, Thorney Abbey accounts 1441-1442 and charters for Woodstone, Fotheringhay College accounts, early 16thC. and accounts of Thomas Wingfield of Kimbolton (Hunts.) 1560-1582