Three I can't parse: 9a As exercise, are volunteers running backwards to get in shape? (13) QUADRILATERAL I get the ARE+TA backwards. 12d Bore keeps going places with wife in London area (2,5,4) ST JOHNS WOOD - why? 19d Modern philosopher from Sorbonne's in revolutionary venture (3,4) NEW AGER) - why?
Qua Drill!? OK re the DRILL but the QUA seems a bit random, But you must be right. I quite like the Johns one, although bore = STOOD is tricky! Many thanks for thise two. Now for NEW AGER...