The haunted eyes of this small boy hold the answer to a mystery that has divided art critics for years.

The portrait, 'One Of Madame Villain's Sons', is of a French child aged about five.

He is reputed to be the illegitimate son of artist Walter Sickert, one of the most outstanding British painters of his age and a close friend of the Bloomsbury set who frequented Charleston Farmhouse at Firle, near Eastbourne.

Duncan Grant and Vanessa Bell, former owners of Charleston, bought the painting in the Twenties and it first hung in the Garden Room in 1939.

But the couple's daughter, Angelica Garnett later removed the picture to her private collection.

The portrait is now once again back at Charleston, bought with grants from the National Art Collections Fund, Victoria and Albert Purchase Grant Fund and the Quentin Bell Commemoration Fund.

The picture, painted in 1904, documents a professional and personal relationship between Grant and Sickert.

Chloe Garner, spokeswoman for Charleston, said: "This is a very dark and moody painting in sombre greys and browns. There has been a lot of speculation over the years as to whether it is Sickert's son or not. I don't suppose it will ever be proved one way or the other."

"Its significance to Charleston is not only that it contributes to the historic integrity of the arrangement of the Garden Room, but it also reflects the taste and status of Grant and Bell as collectors, as well as their artistic affiliations." Charleston's collection includes works by Renoir, Picasso, Matthew Smith and Delacroix.

Next month Charleston is hosting its annual party 'The Quentin Follies' to raise money for The Quentin Bell Commemoration Fund, which aims to reinstate paintings that were at Charleston during Quentin Bell's lifetime.

The party, on July 13, involves a music hall style show and a balloon race, art auction and children's entertainment.

Tickets are £25. For more details, contact Charleston on 01323 811 626.