One of the biggest art exhibitions planned for next year has collapsed because of a row between a European prince and the U.K's HM Revenue & Customs. Masterpieces by Rubens and Van Dyck were among the treasures from the royal family of Liechtenstein’s collection, which were expected to draw huge crowds to the Royal Academy of Arts (RA). But yesterday Prince Hans-Adam II cancelled the loans because a long-running dispute involving export licences and a Spanish Renaissance painting bought in London has not been resolved in his favour.