The rules of the theatrical game have been rewritten

Who would you most like to cast as Prospero in The Tempest? Personally, I'd love to see Helen Mirren in the role. And who might make a tough and charismatic Macbeth? The film star Morgan Freeman, I'd suggest.

Such casting is no longer an idle fancy. We are, I believe, living through one of the most important eras in theatre. When the history of the British stage comes to be written, the summer of 2003 will, I suspect, be seen as particularly significant. Almost by stealth, the rules of casting have been rewritten, not at a few fringe venues, but at some of our biggest institutions.

At the National Theatre, Nicholas Hytner has triumphantly cast the black actor Adrian Lester in a production of Henry V, which has become one of the hottest tickets in town. Down the road at Shakespeare's Globe, the artistic director Mark Rylance has, with far less publicity, been running a gender-swapping season that has seen Kathryn Hunter playing Richard III.

None of this is exactly brand new. There have been black actors cast in traditionally white roles before. And as far back as the Sixties, the National itself mounted an all-male As You Like It. Rylance is far from the first to have played around with gender on stage.

But there's something that separates the Hytner and Rylance ventures from previous experiments. They do not seem like experiments any more; neither audiences nor critics go to see them for their novelty value. Most of the debate about Hytner's Henry V has concentrated on its updating and Iraq war parallels. The fact that Lester, a wonderful actor, is black has attracted little comment. This means, I am quite sure, that we will now see more talented black actors on stage in roles that have been the preserve of their white colleagues.

The Spectator magazine's critic, one of the few who disliked the production, wrote dismissively that Hytner has said he believes in colour blind casting. He put the remark in quotation marks, making it look like Hytner himself proclaimed this. But Hytner does not believe in colour blind casting. From my own discussions with him, I gather that he thinks as I do, and as I have written here before, that it would be difficult, for example, to cast a black actor as a recent historical figure. A black Winston Churchill or Queen Victoria on stage could cause problems for an audience that knows their faces too well. But Shakespeare's characters, even the kings and queens, have a certain mythic quality that transcends historical detail. No, Henry V wasn't black; but nor did he speak in blank verse. Those who insist on accuracy on the first point will have to explain their way out of the second.

But, funnily enough, for me it is not the success in casting Adrian Lester that has the biggest implications for theatre. It is the success of Rylance's gender-swapping season. Fiona Shaw proved some years ago, in her performance as Richard II in Deborah Warner's production, that audiences could accept and enthuse about a woman playing a male role in Shakespeare. But until now there has been little repetition of that experiment. Rylance is right to encourage us to suspend our disbelief further. It is an intriguing exercise for an audience; and how much more intriguing might it be for some of our top actresses.

For, while classic roles tend to dry up for women of a certain age, there's no shortage of them for men of a certain age. Swap the genders and there's a whole new lease of life for our theatrical Dames. Mirren could bring a beguiling worldweariness to Prospero, as indeed could Judi Dench. And that incomparable comic actress Maggie Smith could have her greatest challenge yet. A bit - well quite a bit - of padding, and she could be the greatest Falstaff of her generation.

Suddenly, there is an awful lot that seems possible.

¿ Pride In The Park, Europe's biggest gay, lesbian, bisexual and transgender festival, takes place in Hyde Park this month. The organisers announced yesterday that the rock music event will have a speed-dating arena, and the Rev Pressley Sutherland, the senior pastor of the Metropolitan Community Church of north London, will be on hand to perform commitment ceremonies. Makes Glastonbury look rather staid, doesn't it.

¿ The minimalist production of Stephen Sondheim's Pacific Overtures at the Donmar proved yet another great night of theatre at this small venue. But, reading the programme, I did wonder if the Donmar wasn't overselling its progress. The programme mentioned how Sam Mendes, the Donmar's founding director, and his colleagues had "helped turn a small warehouse in Covent Garden into a worldwide theatrical powerhouse". Come now; this wasn't just a warehouse that Mr Mendes spied while walking round London. It had already been... a theatre, run by the Royal Shakespeare Company. I suppose that "turning a former RSC theatre into another theatre" doesn't sound so romantic.

d.lister@independent.co.uk