It was a juggernaut of contemporary art, with multimillion-pound sales and a roster to die for; Damien Hirst, Jake and Dinos Chapman, Lucien Freud. At the helm of the flagship London gallery in Mayfair, was Harry Blain, a man described as Britain’s number one art dealer. But cracks began to show in the stability of the international Blain Southern gallery. And then last January, just as the gallery reached 10 years in business, the doors closed. One of the artists getting caught up in the mess is the renowned Irish-born artist Sean Scully. Before its downfall, Scully had started to…