I’m often going on about how I don’t see many films but “Whatever Happened to Baby Jane” is an exception. There was a time when it was never off the telly and I remember watching it many times in my youth. That nasty Bette Davis being so vindictive to that lovely Joan Crawford. It was a spellbinding combination.

So what a splendid idea for a play – Miss Davis and Miss Crawford in adjacent dressing rooms on the set of Baby Jane. Their rivalry and mutual dislike is the stuff of legend. The fact that they had “crossover lovers” (as the informative programme nicely puts it) seems less of an issue than their professional jealousies – Miss Crawford the more beautiful, Miss Davis the better actress.

The main problem with the play is the fact that the two characters spend at least 90% of the time soliloquising with the audience. This does allow for one useful and humour-inducing ploy, which is that Bette Davis will tell a story or describe an event in her way to the audience; and then Joan Crawford will separately tell it her way, with the implication that Miss Davis was lying. And later the same thing will happen vice versa. It’s a good comic structure, and you do get the feeling of understanding at least some of the characters’ motivations. But unfortunately it doesn’t really have dramatic tension. The 10% of the time when they’re addressing each other directly is completely sublime. It’s not a bitchathon – it’s subtler than that; exactly the kind of slightly digging, needling conversation you would have with someone you loathe but have to get on with for the sake of the income. It would have been a much more rewarding piece if there had simply been more of this conversation. A lot of the first half feels like it’s treading water. The first fifteen minutes or so sets the scene nicely, but you want things to progress quicker than they do. Certainly the best lines and more revealing characterisation are saved for the second act.

Having said that, it’s an excellent production and the two star turns are exactly that. Anita Dobson arguably has the slightly harder task of portraying Joan Crawford, with her languid tone of voice droning on in that marvellously insincere way. I thought it worked particularly well when she was signing photographs – you realise quite what a horrid Mommie Dearest she must have been. And she issues a lovely telephone threat to her assistant Patricia in the same eerie voice. She also captures Miss Crawford’s artificial smile to a tee which comes to the fore both when she’s being “charming” (deliberately in inverted commas) and also vindictive, as when she’s adding weights to her body so that Bette Davis will put her back out when she lifts her. It’s a superb performance. When she shows her distaste for Miss Davis’ coarseness her face is a picture – not over-the-top pantomime gurning but a genuine gagging reflux look that came straight from her insides. She actually reminded me of a pretentious woman I used to know as a child, which was a surprise. I should also mention that, from my seat in Row C, I would guess I was one of about 6 people that Miss Dobson’s gaze alighted on every so often to look directly in the eye when delivering her monologues. That made me feel really involved!

Greta Scacchi’s performance as Bette Davis is astonishing in every way. With her white make-up, lurid lips and batty wig the similarity in looks to Bette Davis’ own appearance as Baby Jane was remarkable. She gets her clipped, sullen tone absolutely right – she sounds a little angry, even when she’s not particularly. Then there’s also her wheedling voice; beautifully done. For an attractive woman Ms Scacchi can sure make herself look a fright! The script nicely allows for the occasional use of bad language and she relishes every consonant, but you also get a marvellous glimpse of her insecurity and anxiety, as when she deals with her mother on the phone for example. She takes every comic opportunity and makes it work – just her catching sight of herself in an imaginary mirror almost brings the house down. It’s a performance of splendid light and shade, and she’s grippingly watchable.

Rarely seen the Royal Theatre so packed, and the audience loved it. It’s already well into its tour, with just Coventry, Bromley and Brighton to go. It’s definitely worth seeing for these two great performances alone.