Keeping the turbulent backstage goings-on at the court of Henry VIII coherent must have been excellent training for orchestrating the intricately ordered chaos of Mr. Frayn's backstage comedy. While some tightening of a bolt here and a screw there might marginally improve matters, once it hits its lively stride, Mr. Herrin's production rollicks along with machine-tooled precision, churning out belly laughs as if from an assembly line...Dazzling though Mr. Frayn's engineering is, 'Noises Off' would be a mere dissertation in clever dramaturgical mechanics, were it not for the expertly drawn characters, here embodied by a first-rate cast well aware of the addictions, indulgences, pretensions and general egotism of actors (some actors!) that Mr. Frayn is gently playing for laughs.