A rare collection of papers on including letters signed by Oliver Cromwell and Queen Elizabeth I has been saved.
The Westmorland Of Apethorpe archive has been on loan to Northamptonshire County Council's record office since the 1950s.
Now the papers have been saved for the nation thanks to £650,000 grant from the National Heritage Memorial Fund (NHMF).
The archive is based around the correspondence of the Westmorland family who whose country estate was at Apethorpe Hall, near Oundle.
The archive is priceless in historical terms and contains documents from Thorney Abbey, one of the major Benedictine houses of the fens and papers relating to the medieval household of Edward, Duke of York.
The collection, which spans more than 600 years, will remain with Northamptonshire Record Office following its purchase from its private owners.
The money from the NHMF, an organisation set up to save the most precious parts of UK heritage in memory of those who have given their lives for the country, bridges the funding gap to reach the archive's purchase price of £760,000.
A 10-month public fundraising campaign, with a range of events in the Northamptonshire parishes closely associated with the archive, helped raise £45,000 locally.