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
There was success for home grown talent at the MOBOs this evening - as the awards returned to the capital for the first time in six years
A lone Occupy protester who climbed up the Winston Churchill statue in Parliament Square has been arrested - after a two day standoff
Medi Abalimba masqueraded as winger Gael Kakuta to live the lifestyle of a Premier League millionaire after his own career flopped.