A campaign led by the National Gallery and the National Galleries of Scotland to acquire Titian's Diana and Actaeon has been handed a £10m funding boost.

The National Heritage Memorial Fund (NHMF), the fund of last resort for saving great heritage at risk in the UK, announced the award, which will go towards efforts to raise the £50m needed to secure the painting from its current owner, the 7th Duke of Sutherland. In October, the Art Fund contributed £1m towards the campaign, which needs to obtain the necessary funds by the end of the year in order to acquire Titian's masterpiece.

Jenny Abramsky, NHMF chair, said: "We have moved quickly to show our support and hope this persuades others to dig deep and make this dream a reality. It was an extraordinary and challenging decision for us financially, but it's as important as ever to protect our enduring cultural heritage." If successful, it is also hoped that the Galleries will be able to loan the rest of the Bridgewater collection for the next 21 years, as well as being offered an option to buy the Diana and Callisto painting for a similar amount.

The paintings would then go on rotational display between London and Edinburgh for five-year periods at a time.