Around $29m of possessions owned by the Spencer family, relatives of the late Diana Spencer, Princess of Wales, will be sold in London this Summer.
Rubens' painting, A Commander Being Armed for Battle, will take pride of place in the auction with a pre-sale valuation of £8m-12m.
In December last year, a re-discovered unfinished portrait of a lady by Peter Paul Rubens was usurped as the top lot at a Sotheby's Old Master and British paintings auction.
(In the end, the surprise highest-grossing lot was, that sold for an incredible £8.3m.)
Later this year, the Spencers' painting will sell among 600 other lots in the sale according to a statement by Christie's.
The Spencer family's heirloom sale will also include more than a dozen 19th century carriages.
Since 1998, the family's Althorp Estate has hosted its Diana: A Celebration, an exhibition commemorating the Princess of Wales' life.
Proceeds from the sale will fund extensive restoration work to the Althorp Estate.
Naturally, any memorabilia associated with Princess Diana, is both valuable and sought-after.
At present, Diana autographs can command values anywhere from $4,000 to $20,000 or more - with Royal autographs boasting a provenance far superior to other celebrity memorabilia.