Ayckbourn's plays, first seen on Broadway in 1975, are as rueful as they are riotous, a rare combination that has been fully realized here. Their titles _ "Table Manners," "Living Together" and "Round and Round the Garden" _ make them sound as if they are stock sitcoms. They're not.

All three comedies, which are running in repertory, were done last year at England's Old Vic and have been brought to New York with the London cast. Wise move. These six actors give meaning to the term "ensemble," a half-dozen seamless performances that perfectly match each other and the flawless production.

Credit director Matthew Warchus, who has harnessed Ayckbourn's considerable gift for comic mayhem and his penchant for creating intricate, almost mathematically precise plots. That precision is evident in these plays, which take place, more or less simultaneously, over one weekend in three different areas _ the dining room, the living room and garden _ of a comfy rural English home.

Each couple is experiencing difficulties _ all caused by Norman, the trilogy's libidinous title character. Norman is a randy Peter Pan, a perpetual adolescent still in search of his Wendy. And his wife, Ruth, career-consumed and literally shortsighted, isn't enough.

What sets the tale in motion? Norman, a not terribly dedicated librarian, is set to have a weekend fling with his frumpy sister-in-law, Annie. She's in a long-standing but never consummated relationship with a sweet-tempered but dim veterinarian named Tom.

Add to the mix the two women's cranky brother, Reg, and his bossy, pinched wife, Sarah, and you have three couples for whom a weekend together will prove disastrously explosive. What the audience gets from Ayckbourn are different perspectives on those misguided days.

It would be unfair to leave out any actor but the accomplished parade begins with Stephen Mangan as that shaggy lecher, Norman. It continues with Amanda Root, who, as Sarah, raises snippiness to high art; Jessica Hynes, delightfully woebegone as the put-upon Annie; and Amelia Bullmore as Norman's astringent wife. The other men are equally superb: Paul Ritter as Reg, a frustrated estate agent; and Ben Miles as the perpetually befuddled vet.

Ayckbourn's dialogue crackles with the wit of fine British drawing-room comedy, often stinging but anchored in the sharp observations of a playwright who has a generous, forgiving heart for human frailty. Well, at least for everyone except Norman. And, not unexpectedly, a feeling of Chekhovian sadness, floats over the proceedings, too, a realization that life most often doesn't turn out the way you want it to.

Besides its verbal dexterity, "The Norman Conquests" is blessed with some nimble physical comedy: Watch that poor vet sit uncomplaining on the smallest of chairs during a dinner from hell; or as Reg acts out actions the movement of chess pieces while the group tries to play an unbelievably complicated board game he has devised; or as the nearsighted Ruth does battle with a lawn chair _ and loses.

In London, the Old Vic's legendary proscenium auditorium was converted into an in-the-round theater, something already in place at Circle in the Square. The plays fit snugly into the space, bringing the audience almost into eyeball proximity with all the addictive, onstage tribulations.

Seeing one play in "The Norman Conquests" is a pleasure. Watching a second is even better. Add a third and you will get the full force of Ayckbourn's expert theatrical delirium.