Arcadia, on the other hand, is another matter. Tom Stoppard's ingenious collision of literary biography with chaos theory in a Derbyshire stately home is being broadcast on Radio 3 next Sunday, with the same cast that opened it at the National Theatre this April. The attraction of this transfer is obvious: for a start, you have a cast that knows the play back to front. David Benedictus, who directed the radio version, says that, 'If one was starting from scratch, one wouldn't have that cast: I don't think one could afford it.'
But there were disadvantages, too. Stoppard himself minimises the differences between the play on stage and on radio: 'Character is what people say, not what people look like.' Benedictus, who had to cope with the play's time-scheme - flipping between 1809 and the present - is less blase. He is still unsure that the action will be as explicit for the listener as it was for the viewer.
The actors, too, have had their share of troubles. Bill Nighy, who plays a 20th-century academic researching Byron's doings in the Derbyshire of 1809, has done plenty of radio work. This was a new challenge, though. He had to abandon timing built up over months of knowing when the audience was going to laugh, and a physical identity he had created for the character. He also had to find an entirely new level of performance: 'I walked in, walked up to the microphone, started to do it as I do it on stage, and nearly blew the speakers.' Once he'd turned down the volume, 'Quite quickly it became an advantage to just talk to someone in a naturalistic way, rather than in a theatrical setting.' Emma Fielding, who plays a 13-year-old mathematical prodigy in the 19th-century scenes, found that the intimacy of radio helped her on stage: 'It's back to the rehearsal room: you rediscover things that you've lost sight of with a large audience.'
In the end, the justification for the radio production is not what it does for the actors. Benedictus puts his finger on it: 'More people will get to hear it on that one radio transmission than will have seen it all year . . . A radio production is a very good way of making the National Theatre a national theatre.'