"The Lock." (Courtesy The Guardian)

Tomorrow, Christie's London will sell John Constable's The Lock (1824), which is expected to make between $31 million and $39 million and has a shot at becoming the most expensive work by a British artist ever sold at auction.

It's not all sunny, though. The Daily Telegraph reports that the painting's seller, Baroness Carmen Thyssen-Bornemisza, a 69-year-old firecracker who goes by "Tita," has caused headaches in Spain over her decision to sell the work due to "liquidity" problems.

The move caused Sir Norman Rosenthal, former exhibitions director at London's Royal Academy, to resign as trustee of the Madrid museum.

Tita still owns some 250 private works that she loans freely to Spanish institutions, but, Sir Norman wrote in the leading Spanish daily El Pais, "I am afraid I have to say in my humble opinion she has little or no understanding of art history or of genuine artistic importance in the context of the museum."

Worse still, she may not even make a profit! The Financial Times recently concluded that, taking into account inflation and the insurance costs, the painting would have to sell for $93 million or more to mean a return on investment for Tita.