When the Broadway producer David Merrick "invented" critical plaudits in a full-page ad for his feebly reviewed 1961 show Subways are for Sleeping, the stunt backfired, the phoney blurb making only one edition of one newspaper before it was withdrawn.

Merrick had found seven names in the Manhattan telephone directory that corresponded exactly with those of the seven leading Broadway critics and invited the owners of them along to the show, teasing out critically enthusiastic responses (they'd been given free tickets) and permission to be quoted.

Now that everyone's a critic, apparently, the producers of The Book of Mormon have pulled a similar trick in both this week's Sunday Times Culture section and today's Guardian, quoting accredited tweets not of critics but of ordinary punters at previews.

One of them says it's the best thing ever on the West End stage, another "I practically peed my pants" (not a phrase often associated with Michael Billington), another, "The cast sooo do justice to the writing" (move over, Libby Purves), yet another, "Bruised my hands clapping so much last night" (take that, Tim Walker).

Quotes are just quotes and these look no worse or any sillier than "A masterful performance" or "The best play in the West End" from, say, Mark Shenton's Sunday Express review of Quartermaine's Terms. The difference is that a critical tweet comprises just 140 characters whereas a bona fide critical quote comes from a longer article, presumably argued from a professional, informed and paid-for independent point of view. Who are you gonna trust?

I would have thought that the advertisement standards authority might be interested in these Mormon blurbs. To me, they smack a bit of desperation, as if the producers are not sure if the cult status of the show, and its obvious appeal to people who watched things like The Simpsons and South Park on television (ie, a minority audience), will convert into popular long-running West End material.

We shall see, but not as soon as we thought, as the first Press invitation to tomorrow's preview performance (with all reviews embargoed until next Friday) has now been withdrawn, on the grounds that the show's not ready yet - though ready enough for gleaning power-to-the-people opinion, apparently. I would have thought this ruse now entitled critics to write about the show whenever they damn well please; in fact, one or two already have, in the guise of somewhat over-friendly feature articles.

Back in the normal world of fringe theatre endeavour, I made only my second ever trip to the delightful Rosemary Branch Theatre in one of the most interesting patches of Islington last night: right down by the Regent Canal at the end of a street - Shepperton Road - of quite extraordinary double-fronted mid 19th century town houses.

The show was Promise, an American war-time re-write of Three Sisters. Olga, Masha and Irina have, in fact, become the Andrews Sisters in rural Nebraska; Vershinin, still "the love-sick major," a balder Brooklyn sidekick of Phil Silvers as Sergeant Bilko; and the doctor who falls off the wagon on the night of the fire (or, in this case, the snow storm) a fairly bland jollying-along sort of uncle, though nicely played by Nick Simons.

Most of the actors are recent graduates from Drama Centre. One of them, Sophie Angelson, has done the script and plays Irene (Irina), a bright-eyed girl in the telegraph office who dreams of getting to New York - not as difficult as all that, surely, even in war-time - plays the piano and dances cheek to cheek like Ginger Rogers.

It's all fairly well done, but it lacks the punch, scathing intelligence and experimental panache of Benedict Andrews' brilliant version of the same play at the Young Vic last year.

This is the dilemma for classics on the fringe: what's the point unless you have one to make? Strindberg's Miss Julie is probably one of the most over-adapted classics of modern theatre, but the scintillating new South African version at the Riverside Studios this week proves that you really can re-define great drama on your own terms if your passion and skill are a match, or a close fit, for the original dramatist.