First Night: Phedre, Ritzy Cinema, Brixton

Dame Helen Mirren playing Phedre, the classical theatre's most ardent lover, pulsating with incestuous desire for her stepson, Hippolytus, played by the Mamma Mia! heart-throb Dominic Cooper, is the definition of a hot ticket. Naturally, the National Theatre production sold out in hours. Last night, though, those not lucky enough to have a seat at the Lyttelton Theatre had an alternative – when the live performance was beamed by satellite to 70 cinemas across the country, from Glasgow to Guernsey, and a further 200 worldwide.

As an intriguing cultural concept, would it work? Would the actors falter, caught between projecting to the gods and caressing the lens? And would the audience crunch on popcorn as they watched Mirren in her death throes? The answers were: very nearly; not for a second; and yes (but guiltily). NT Live is a bold innovation. The New York Met has been selling out screens with its live opera broadcasts since 2006. The Royal Opera House followed suit last September, adding to its free outdoor summer shows in Trafalgar Square and other city spaces which have been running since 2000.

Ticket sales (at £10 a time) for last night's Phedre topped 30,000 worldwide with Picturehouse cinemas in Oxford, Henley and Norwich laying on a second screen owing to demand. Touring rep theatres could not reach so many people, and filming plays for television has often been a rather static approximation of the excitement of the live stage.

At the Ritzy in Brixton, the atmosphere was one of cautious excitement and curiosity. "We both go to the National a great deal and couldn't get tickets, so we've come to this instead," said Eliana Steel. "It's very good value for money too," added her companion Julia Stafford-Northcote. Settling down with a bottle of Stella Artois to watch, Jenny Trevor said: "We usually miss the boat. By the time we've heard about plays they've completely sold out." Her husband Nick was missing his office summer party for the event. "I told my boss it was because I was going to see Helen Mirren and he said, 'well, I don't blame you'."

Last night, there was not a hint of aspic about the performance. From the moment the curtain rose in the theatre, and the coughs from that auditorium were broadcast into the cinema, it all felt thrillingly live and alive. The excitement was in seeing the actors, if not in the flesh, then in intense close-up, from the veins in Cooper's neck to Mirren's rather un-regal and anachronistic tattoo on her hand. Every fleck of spittle and bead of sweat was picked up.

It felt a little strange. The "trailers" beforehand – video interviews in which the National's artistic director Nicholas Hytner told us "the actors have succeeded magnificently" were off-key and debunked the magic of theatre unnecessarily.

And while Bob Crowley's set, a pock-marked cavern set against a cerulean blue sky probably looked magnificent from the stalls, some of the shots made it look as though the actors were acting against a blue screen. Acoustically, Mirren was a little muddy at first but every word was clear – which is not always the case at the back of the circle.

A fundamental problem of filming is that someone else is choosing what you see: occasionally I longed for the camera to track away from Mirren for a moment and show the reactions of those around her. But it also revealed lovely nuances – the stiffness of Cooper's spine when Mirren, declaring her foul love to him, writhes around him, as well as her waxy complexion and dead eyes as she made her final speech.

At the end, the Ritzy's audience politely joined in the applause as it echoed around the actors on stage. No standing ovations but a significant success. How many Dr Who fans would have relished the chance to see David Tennant as Hamlet in the same way? I left wishing I could have seen the performance in the flesh but, for thousands disappointed at the box office, this is the next best thing.