Joseph Beuys: multiples were a key component of Beuys’ output; ‘The objects are understandable in relation to my ideas’, he said and, in this exhibition of some 300 of the multiples, most come with long explanatory captions. At first this is irritating. Many relate to performances and, with work that is so self-referential and relies so heavily on personal mythology, the exhibition becomes like a display of holy relics. Beuys was definitely sincere but now that he is no longer here to charm us with his circular arguments, the work can seem wilfully arcane and self-regarding.