Knole House in Sevenoaks, Kent, is to receive £7.75m for repairs and conservation from the Heritage Lottery Fund.
The funding will also go towards the construction of new visitor facilities at the 15th century medieval palace, a former hunting lodge to Henry VIII.
The National Trust said that since acquiring Knole in 1946, it had faced expensive running battles with rain, damp, mould and insects, but the funding meant the future of the mansion and its treasures were now secure.
More top news
Hertfordshire based eBay seller relists ad for the car that "ruined her life" after the auction website deleted it for swearing.
The accident happened on Clapham Road at lunchtime.
Tower Hamlets tops the league, with the population set to soar 25% by mid-2024.