The Heritage Lottery Fund (HLF) has come to the rescue of the Watts Gallery in Compton, Surrey, which, officials say, needs almost £10 million to safeguard its future.
The gallery has earmarked the windfall for the repair of its leaking roof and restoration of the fabric of the building, which was built in 1903.
Gallery chiefs are in the process of choosing an architect, and hope work will be able to start in spring 2008.
The building was originally constructed to house works by George Frederic Watts, at the time one of the country's most celebrated portrait painters, and still displays an array of Victorian art treasures.
A spokesman for the gallery said: 'We are thrilled that the love and affection in which the gallery is held both in this country and abroad, the international significance of the collection, the beauty of the building and its setting, and its extraordinary role as a national gallery in the heart of a village, has been recognised by the HLF.'