NEW YORK (NYT) - A legal dispute has revealed that a painting thought to be the world's most expensive artwork is not the most costly one after all.

Paul Gauguin's 1892 oil painting Nafea Faa Ipoipo (When Will You Marry)? sold for US$210 million (S$290 million) in 2014, US$90 million less than originally reported.

The New York Times and other news outlets reported in 2015 that the painting had been sold by Mr Rudolf Staechelin, a retired Sotheby's executive, to a Qatari buyer for close to US$300 million. If true, that would have been the highest known price for a painting.

Prices in private sales of artwork are often closely guarded secrets, particularly when they reach astronomical levels.

On Wednesday, however, a trial - over the commission - began in the High Court in London that revealed the ins and outs of this particular high-stakes art deal, which took nearly two years of negotiations to complete.