Spencer nets $19m but is it a Rubens?

Leading art historians have cast doubt over the authenticity of a £9 million ($19.07 million) painting attributed to Rubens, which was sold by the family of Diana, Princess of Wales, last week.

Portrait of a Commander Being Dressed for Battle was the star lot in a three-day sale of chattels from the Althorp estate held by Christie's, which netted £21 million for Earl Spencer, the house's owner and brother of the late princess.

Sotheby's, a rival auction house, had initially been offered the sale, but did not go ahead after an external art consultant refused to confirm the painting's provenance. A spokesman for Sotheby's declined to discuss the matter, saying: "Sotheby's never comments on sales it doesn't conduct."

Although £9 million is the second highest price paid for a work by the Flemish master Sir Peter Paul Rubens, the painting only reached the lower end of its estimate, which was set between £8 million and £12 million.

Brian Sewell, a leading art historian, added to speculation it might not be a Rubens, calling it "an uncomfortable Rubens".

"It's one of those pictures that doesn't quite ring true. It doesn't surprise me Sotheby's turned it down. I know from my own experience working at Christie's that you very quickly cause grave offence if you express doubts to people who think they own a genuine painting by an old master."

A spokesman for Christie's said the auction house had undertaken rigorous research to confirm the painting's provenance, and it had been vouched for by a panel of academics. However, an outline of the painting's provenance in the catalogue is thick with caveats, almost every paragraph starting with the word "possibly".

A fuller description of its provenance reveals that opinion has been consistently divided, and for nearly 100 years it was attributed to the "school of Pourbus". Only after World War II, in an exhibition of pictures from Althorp at Agnew's, was it fully attributed to Rubens.

Sewell, art critic for the London Evening Standard, said that authenticating pictures was one of the main difficulties faced by auction houses.

"It's a moral dilemma they face so frequently. Is it the job of an auctioneer, as the mere engineer of a sale, to express his doubts? ... I think anything under £20 million is cheap for a Rubens."

The portrait, bought by an anonymous buyer, was one of 775 items sold by the trustees of the 5665ha Northamptonshire estate to raise money for essential work needed on the house.

- INDEPENDENT