From Althorp, the family home of Diana, Princess of Wales, 775 items were sold at Christie's in London last week for £21m. The top lot was Portrait of a Commander Being Dressed for Battle, by Sir Peter Paul Rubens, which reached £9m ($13 million), the second highest price paid for a work by the Flemish master and just over its low estimate.

On Sunday, the UK's Independent cast a shadow on the Rubens with a report that Sotheby's had initially been offered the portrait for sale, but an unidentified outside consultant for the auction house would not confirm the provenance which was riddled with "possibly" ownerships.

Art historian Brian Sewell, who called it "an uncomfortable Rubens " was also among the experts fueling doubts about the attribution of the portrait.