Soapbox: Are gentlemen’s agreements still valid in the art world?

A precedent-setting legal dispute over a $10m (£7.2m) fee relating to the 2014 sale of a $210m Paul Gauguin painting was won by auctioneer-turned-art adviser Simon de Pury last week, despite him only having a gentleman’s agreement. We ask whether such agreements are still valid in today's art market?