Established 32 years ago in Salzburg, the Hagen Quartet can fairly be described as venerable. It may be said equally fairly that brothers Lukas and Clemens Hagen, their sister Veronika, and Rainer Schmidt, are playing better than ever. The opening pair of concerts in their Beethoven cycle at Wigmore Hall in January were remarkable for the freshness as well as the beauty of their playing, and their return next week (19 and 20 April) to the world’s greatest hall for chamber music should not be missed.