ALAN Ayckbourn’s 73rd play carries a warning. “Be prepared to be appalled!” he says at the end of his programme notes.

“We choose to talk or behave in front of children entirely at our own risk. By them shall our inadvertent utterances and actions later be judged, avoided, or God forbid, on occasions emulated.”

Ayckbourn has been watching his unsuspecting fellow man from the age of four, when he would sit in the corner of rooms as a “tiny invisible war correspondent, silent and inwardly digesting”.

For young master Ayckbourn, read one Winnie Barnstairs, nearly nine and off sick from school for the day, a day she will spend recording everything around her for her essay My Wonderful Day. Winnie (the remarkable Ayesha Antoine) sits, often silent and invariably unnoticed, as her very pregnant mother Laverne (Petra Letang) tends to her cleaning chores at the fashionable North London home of boorish television personality Kevin Tate (Terence Booth).

Today is Tuesday, the day each week when Winnie and Laverne will speak only in French to help her schooling: the cue for yet another source of comedy from Sir Alan, who continues to find new ways to entertain, keeping us onside while reminding us of our ceaseless fumbles, failings and foibles.

He does so here by filtering everything through the ever-alert eyes of a young girl, so we can laugh at our weak, rotten, self-absorbed selves. Into the house come Kevin’s dippy secretary and totty on the side Tiffany (Ruth Gibson) and his lugubrious, bleary-eyed friend Josh (Paul Kemp). Towards the close, once Laverne has been sped away to hospital, Kevin’s BAFTA-winning, cheated wife Paula (Alexandra Mathie) arrives in volcanic mood, brandishing the sharpest lines of a play whose momentum is all the better for Ayckbourn foregoing an interval.

Ayckbourn is on top form here – 50 years on from his first play The Square Cat – in his devilishly witty writing, casting and direction. His use of French and long silences and a scene where Winnie reads a passage from The Secret Garden to a snoring Josh all add to his long history of theatrical risk-taking, while he applies Mick Hughes’s lighting and the theatre-in-the-round’s exits brilliantly to create the sense of moving from room to room and to set up action off stage.

His social commentary has renewed bite too, Ayckbourn taking a swipe at soulless city developments in an advert for Fantacity, and issuing a cry from the heart about the loneliness of boarding schools.

After his superlative revival of How The Other Half Loves this summer, Ayckbourn triumphs again with his wonderful new play. Next stop, New York in November.

My Wonderful Day, Stephen Joseph Theatre, Scarborough, until October 31. Box office: 01723 370541.