Christie's auction house said Monday it will sell about 20 million pounds ($30 million) worth of artifacts fro
m Althorp House, in Northamptonshire, central England.Althorp is the home of Diana's brother Earl Charles Spencer, who recently announced his engagement to Lady Bianca Eliot.
The Rubens portrait - "Commander Being Armed for Battle" - has been owned by the Spencer family since 1802.
Other lots include a painting by Giovanni Francesco Barbieri and 19th Century horse-drawn carriages.
Three auctions will take place during the summer.
