We made a lightning dash to Brussels to attend the first night of Pierre Audi’s production of Alcina, designed by Patrick Kinmonth.   First performed some time ago in Drottningholm, revived in Amsterdam, and now renewed for La Monnaie, it has been designed and staged much more authentically than would now be normal in London, with a fine eye for eighteenth-century detail, based on the paintings of Devis (and maybe a bit of David).   The second act, in particular, was extraordinarily powerful:  beautiful music, beautifully staged and, above all, beautifully sung by Sandrine Piau as Alcina.