Even at 90, the conductor Sir Neville Marriner was not too senior to bring to the Proms last Sunday afternoon the Academy of St Martin in the Fields, the small orchestra which, as a violinist, he had founded 56 years ago to play in the confines of the eponymous Trafalgar Square church. His idea, revolutionary in the 1950s, was to revert to eighteenth-century practice and direct with his bow, rather than conduct with his baton, from the leader’s chair. Thus it was only slightly unexpected when the orchestra started playing as soon as the current director, Joshua Bell, had sat down and nudged it in with his shoulder. Without a conductor, players are more reliant on their ears to maintain ensemble, which in Beethoven’s First Symphony was electrifying. One current coursed through