The wonderful thing about theatre is its unpredictability. Millions of pounds can be poured into a show that will flop and equally, a small scale production can catch the imagination of the public and soar to be a great box office hit.

I had never heard of Florence Foster Jenkins when the publicist mentioned her to me a few weeks ago but her story was interesting. She was a rich, eccentric American woman who couldn’t sing but who became something of a cult and ended up singing in and filling the Carnegie Hall. My research took the form of playing samples of her cds on the Amazon website. They were hysterical. I laughed and laughed at the quirkiness of this so-called “soprano of the sliding scale”. Soon I was dining out on Florence’s joyously off key singing. Even my cats liked it. How could one woman bring so much more pleasure than the talents of the great tenors combined? When I read that what she heard inside her head was perfect pitch, I found it all the more endearing.

So now two plays about the glory of Florence Foster Jenkins entertain London and Broadway at the same time. In a masterstroke of casting, the delightful Maureen Lipman has been chosen to play Florence in Peter Quilter’s play which premiered at Birmingham Rep two months ago. It opens with Florence interviewing a prospective new pianist, Cosme McMoon (William Oxborrow) who has to make the difficult decision whether to continue playing “hidden behind the salad, obscured by broccoli” in a restaurant or to compromise his musicality by linking up with this unmusical lady. Her charm wins him over and his narrative description of the Carnegie Hall triumph and her death within five weeks of that concert is a touching finale.

As Florence says, “The world first heard my voice in 1912, the year the Titanic went down.” I suspect that the British audience’s reaction to Madame is similar to the original. They cheered and clapped and shouted, “Bravo!”. Any tears were not those of emotion but because we were helpless with laughter. When at one point, a rare detractor, Mrs Verindah-Gedge (Lolly Susi) claiming to be a representative of the Music Lovers of America, mounts the stage, she is booed and there are shouts of “Off!”

Peter Quilter’s is not a one joke play. Besides the gay and sensitive pianist Cosme, the excellent supporting cast feature Maria (Janie Booth), Florence’s excruciating and insubordinate Mexican maid, her friend the equally batty Dorothy (Josie Kidd) with a bizarre pet poodle and of course the British actor who describes himself as Madame’s boyfriend, suave St Clair (Barrie Ingham). But the acting honours go to Maureen Lipman who has captured Florence’s amazing staccato delivery. Ms Lipman has to be padded to achieve the rather rotund Madame Jenkins’ shape and the designer has been able to clothe her in truly over the top stage wear. Her flamenco outfit, rather like an elaborate and overdecorated red christmas cracker with every flounce, frill, lace and pompom is smashing and when Lipman gets her mantilla in a twist so that it falls over her face and her castanets tangle mid strut, the result is unforgettable.

Discovering in a car accident that she can hit F sharp several notes above high C, she continues to access the note onstage by hitting her forehead in a recreation of the collision. Florence’s irony is quite delicious, “I bet Nellie Melba never had to put up with this!” she says, while her critics say cryptic things like “You will never hear a voice like this at Carnegie Hall again!”

There is an atmospheric gauze screen with projected vintage monochrome film of New York traffic from the 1940s and, during the scene changes, we are played some lovely (and in tune) classical music. The set starts with Florence’s overstuffed New York apartment but metamorphoses into the balconies at the Carnegie Hall. Director Alan Strachan has timed the Glorious! comedy to perfection. The skill is in our not feeling that we are being unkind when we laugh at Florence, but relaxed that, for whatever reason, she is enjoying the pleasure she brings. It is a charming night out which reminds us all what it is to dream.