The Royal National Theatre officially celebrates 25 years on the South Bank this week, on Thursday 25 October 2001, with publication of a commemorative book, a special photographic exhibition, the reunion of three NT artistic directors - former chiefs Peter Hall and Richard Eyre as well as current director Trevor Nunn - for a special platform event, and, last but by no means least, a unique chain play written by 25 theatre luminaries.

Founded in 1963, the National Theatre was initially housed at the Old Vic Theatre, with Laurence Olivier at the helm. It moved to its purpose-built complex, designed by architect Denys Lasdun, in 1976. Since then, the NT has presented more than 400 plays in its three performance spaces - the Olivier, Lyttelton and Cottesloe.

A new book, In Rehearsal at the National, a co-publication with the NT and Oberon Books, presents a chronology of NT programming and, in over 200 black and white photographs from the NT Archive, captures preparations for many of the theatre's most famous productions. The pictures track the career development of some of the greatest names of the modern stage, including: Simon Callow, Judi Dench, Ralph Fiennes, Albert Finney, Michael Gambon, John Gielgud, Peter Hall, Anthony Hopkins, Felicity Kendal, Ben Kingsley, Jude Law, Arthur Miller, Harold Pinter, Vanessa Redgrave, Miranda Richardson, Paul Schofield, Simon Russell Beale, Antony Sher, Maggie Smith, Tom Stoppard and Zoe Wanamaker.

In Rehearsal at the National is launched at the NT on Thursday afternoon, with a speech by Simon Callow. It coincides with the opening of an exhibition of pictures from the book in the Olivier Foyer. Later that day, the three artistic directors - Hall, Eyre and Nunn - will host an hour-long discussion, looking back on the history of the country's flagship theatre, as well as assessing its role for the future.

Finally, the most ambitious element of the NT25 celebrations has got to be the Chain Play. Twenty-five playwrights who have featured in the National's evolution have participated in the unique piece, with each writing one scene and then handing on to the next to develop, with complete freedom, as they see fit.

Internet-friendly theatregoers have been able to track the play this month, with a new scene being posted each weekday on the NT website. Although, so far, the identity of each scene's author has remained anonymous, the list of confirmed contributors reads like a who's who of modern playwriting. It includes: Sebastian Barry, Simon Block, Moira Buffini, Nick Dear, Kevin Elyot, Tanika Gupta, Lee Hall, Zinnie Harris, Jonathan Harvey, Terry Johnson, Charlotte Jones, David Lan, Patrick Marber, Frank McGuinness, Stephen Sondheim and Shelagh Stephenson and Colin Teevan.

With such eclectic input, the piece has, unsurprisingly, taken many peculiar twists and turns. From its naturalistic and lurid opening scenes about the lives of petty criminals on the "Costa del Europe", it has dramatically moved on, bringing in elements of Pirandello, Priestley and Brecht and including visitations by Gods, angels and a man in a trilby.

Some observers have already guessed the creators of certain scenes, not least Scene 12 - a musical finale to Act I, written by a New Yorker, responding to the 11 September events in that city. The song is an adapted version of "Something Just Broke" from Assassins, a song that was cut from the original American production and restored for the London outing at the Donmar Warehouse.

The still untitled NT Chain Play will receive its first, and probably only, performance on Friday, 26 October 2001. The piece will be directed by John Caird. Casting has not yet been announced.

- by Terri Paddock