Brangh in the near-sell out Edmond

The Olivier theatre, currently showing David Mamet's Edmond, has been more than 90% full for most performances in the last few weeks.

More than a third of people who bought �10 tickets for the performance of Henry V were first-time visitors to the theatre.

The National's director Nicholas Hytner introduced the �10 tickets to boost sales and to attract a younger audience.

He says the fact that programme and catering sales are down is proof the theatre is attracting a younger, less affluent audience.

Critics of the �10 ticket scheme have said they suspected the cheap prices would only encourage rich people to go to the theatre more often.

'Hytner effect'

A similar �10 scheme has also been introduced by the Royal Shakespeare Company for a week-long period.

Despite the success, Mr Hytner has said he is terrified of talk of a "Hytner effect".

"There's always a law of theatrical gravity: what does up will go down," he told the Guardian newspaper.

He added: "The great thing is never to feel too pleased with yourself."

A spokeswoman for The National Theatre told BBC News Online that there were only a few tickets remaining for matinee and evening performances of Edmond, starring Kenneth Branagh, still available over the coming weeks.