Sardonic and volatile, David Tennant's Hamlet was so graceful that at times he seemed almost to dance across the stage. The idea of seeing Dr Who in the flesh brought schoolchildren thronging into Gregory Doran's modern-dress production for the RSC two years ago. What they saw was a japester who pushed himself squealing along on a caster chair, a young man sunk in a melancholy dream and a prince of parody, a compulsive mimic who kept becoming someone other than himself. This was a Hamlet who continually played with the idea that wit can look like witlessness. And vice versa.