Desmond Barrit: 'Im making a Habit of being Richard Griffiths

It is slightly frightening seeing a show when you know you are going to take over a role. Actors are like magpies – they pick everything up that they think is clever. Of course, you want to reinvent a role and not repeat what the previous actor did. The fact I have taken over from Richard Griffiths twice – both in The Habit of Art and The History Boys – mystifies me because we are very different.

The Habit of Art is a play within a play. We are playing a character called Fitz, who is an actor and who is playing W H Auden in a play about Auden and Benjamin Britten. So Richard played Fitz, I imagine, as Richard sees him, and he played Auden how Richard would interpret Auden, whereas I play Fitz as Des, and play Des's version of Auden.

A very good director, if he really loved what the original actor did, will have you reproduce almost exactly what he did – but incredibly subtly. One of the good things about taking over a role is that some of the more mundane elements of rehearsals are taken out of the equation. In an original production there is a lot of working out where to stand. There was a lot of that in The History Boys with all the boys and chairs and tables. If you take over a role, all that to-ing and fro-ing is already resolved, so you just stand where you're told.

The most difficult thing about taking over in a show that's a huge success like The Habit of Art is always to make sure you live up to the original.

'The Habit of Art', National Theatre, London SE1, 15 July to 31 August in rep, then touring (Nationaltheatre.org.uk)