In common with many older members of the audiences piling in to see Equus at the Gielgud Theatre at present I have vivid memories of it 'the first time round'. John Dexter's 1973 production of Peter Shaffer's play for the National Theatre remains firmly imprinted on people's minds largely, I suspect, as a consequence of John Napier's designs, which he has 'revived' - if that's the word - for the latest show. The peculiar awfulness of the crime at the centre of the drama - the blinding of six horses by tortured teenager Alan Strang - also makes for lingering memories.

That we have had to wait so long for a major professional revival is said to be explained in the reluctance of Shaffer, who is now in his early 80s, to see another actor take on the role of Strang, which had been so brilliantly created by Peter Firth (pictured in rehearsal above). In a programme note Shaffer explains: "It wasn't a specific decision not to do the play. But it's true that I didn't feel especially enthused about anybody doing it again. Then it occurred to me that there must be a lot of people, especially young people, who had probably never attended a professional production of Equus and I began to feel a tremendous desire to see the play once more." In respect of the casting, he adds: "Whoever plays Strang doesn't have to be 17 in reality but he does need to be able to convey a rawness, an impressionability and a sensitivity."

These qualities, I feel sure, he must be detecting, just as I did, in the fine performance by the Harry Potter star Daniel Radcliffe - as I did, too, in the first stage Strang I saw. This was not Peter Firth, who by the time I got tickets to the play at the Old Vic had gone off to join the Broadway production (in which Alec McCowen's part as the psychiatrist Martin Dysart was played by Anthony Hopkins). Firth's replacement was Dai Bradley who had previously made a name for himself as a young falconer in Ken Loach's Kes. In fact, being in the film had actually given him a name: David Bradley, as he was previously known, had to become Dai to avoid confusion with the British actor who is well known these days as the nasty Hogwarts groundsman Argus Filch in the Potter movies.

'My' Dysart was Colin Blakely, whom I had seen the previous year in the West End in Christopher Hampton's adaptation of Henrik Ibsen's A Doll's House, which starred Claire Bloom as Nora. Blakely was later to take on the role of Strang's dour, porn-film-visiting dad in Sidney Lumet's 1977 screen version of Equus, in which Richard Burton played Dysart and Peter Firth reprised the role of Alan. His 'love interest' on this occasion was Jenny Agutter, whose switch from the innocence of The Railway Children to full-frontal nudity here was almost as startling as Daniel Radcliffe's reinvention as a raunchy pin-up boy. Thirty years on, Jenny now portrays the kindly middle-aged magistrate who puts Dysart on to Alan's case. How long ago it all seems . . .