Les Miserables is possibly the musical that got me interested in musicals. Having seen the perma-touring production in Edinburgh's Playhouse as a child, being weaned on a strict diet of the 10th Anniversary Concert from the Royal Albert Hall on video at my grandma's house and now carrying the London cast recording with me everywhere on my iPod, you could certainly say I am a bit of a fan. You might then think that I had died and gone to heaven, seeing two incredible productions of the musical in one weekend. You might be right.

I might have managed to get myself out of bed and all the way to the Barbian for the 10.30am performance on Saturday morning, but the show stopper was, of course, the 25th Anniversary Concert at The O2 arena last night. I arrived to find the matinee performance just clearing, with nearly every theatregoer I passed proudly toting their tome-like programmes in Les Mis carrier bags. This was no ordinary trip to the theatre. This was a 20,000-strong capacity crowd going to one of the UK's largest arenas... to watch a musical.

They often say that theatre, as opposed to film, is the actors' medium. However, as with most large-scale concerts, the action last night was dictated by the video director rather than what the actors happened to be doing. Three massive video walls dominating the back of the stage, occasionally used to set the scene, interspersing video of what looked like came from the Barbican production or the occasional watercolour of the French countryside or a Paris street, there was also a recreation of that all so impressive melt downwards into the Parisian sewers after the fall of the barricades.

Although brought to the stage by the creative team behind the the Barbican and new European touring productions - directors Laurence Connor and James Powell - this was a rendition of the traditional Les Mis, the Les Mis of the London cast recording and of RP and Cockney accents. None of the tour's edgier northern twangs were detectable here, neither were the slightly rockier orchestrations, but that wasn't what we needed or wanted: we had a full concert orchestra and a 200-strong tricolour-clad choir to bring the score to life.

Alfie Boe as Jean Valjean gave as operatic a performance as one would expect from the tenor, his voice resonating around the The O2 and only adding to the vibrato. Katie Hall continues in the role of Cosette she had perfected in appearances at both the Queen's and 25th Anniversary productions, whilst Ramin Karimloo, taking time off from playing the Phantom in Love Never Dies made a formidable Enjolras. I found Matt Lucas' performance as Thenardier pedestrian, and although an obvious comic, I didn't really know why - when surrounded by superstars of the West End and Broadway - he was actually there, or for that matter why he commanded such a large round of applause upon his initial entrance.

The performances of Norm Lewis and Lea Salonga brought a distinctly American voice to the evening, but few performances of "Stars" can be more impressive than the one we witnessed, with Norm set against the entire back wall of The O2 lit by starcloth.

Nick Jonas sings like the performer he is - a Disney stuffed shirt, with a voice which makes one think he has never once been dispatched to a stage without the aid of a microphone. The majority of his performance was passable, his duets with Katie Hall and Samantha Barks were all there vocally, but his rendition of "Empty Chairs at Empty Tables" might have been the only disappointing moment of the night.

In a space the size of The O2, theatregoers were always going to be at the videographer's mercy - however Samantha Barks and her performance of "Own My Own" really showed off the power of the concert format which had been created.

With the set dotted by backlit slatted windows, mirrored on the video walls above, Barks stood as a lone figure on the massive stage. Once the camera had finished its sweeping and cross fading trickery, reminiscent of a live episode of X Factor, what emerged was a head and shoulders close-up, beautifully framing her performance. The combination of her voice, the staging's design and the power of the video to bring you close to the performance really did combine into something mesmerising.

One thing I began wondering as the concert drew towards its inevitable close was just what Cameron Mackintosh could have planned to out-do his 10th Anniversary Concert at the Royal Albert Hall. In 1995 the stage was stormed by no less than 17 Jean Valjean's from productions around the world marching in full evening dress with their countries flags, singing snatches of "Do You Hear the People Sing" in their native tongues. As small specks of confetti had been dropping from the roof throughout the evening we knew that a fanfare was on its way, but quite what it would accompany was still a mystery.

The answer, what Mackintosh referred to as the "Company of Companies", was well worth the wait: the cast of the production which has toured the UK, "coming home" to the Barbican after 25 years and soon heading for Europe; the cast of the Queen's Theatre show, a constant fixture of Shaftesbury Avenue and the West End's longest running musical; the London company which created Les Miserables way back in 1985; and the assembled O2 concert cast all took the stage together. The best bit was they each brought a Jean Valjean with them!

Having created the role, there is no denying that Colm Wilkinson is the voice of Jean Valjean. His effortless falsetto for "Bring Him Home" has to be the reference for every subsequent performer. Although Alfie Boe did a sterling job, the only person I have ever sing it as well was John Owen-Jones at the crack of dawn on Saturday morning at the Barbican.

The highlight of the entire evening for me was to hear the four Jean Valjean's (Colm Wilkinson, John Owen-Jones, Alfie Boe and Simon Bowman) perform "Bring Him Home" as a quartet. Even aged 66, Wilkinson gave the other three tenors a run for their money and he seemed to be loving every minute of it.

A performance of "One Day More" followed from the cast of 1985 and every one of them proved that a quarter of a century on, they've still got it. Watching Michael Ball's Marius was a particular pleasure.

In a short and well deserved speech, Sir Cameron took the opportunity to praise the the casts of a show with whom, he admits, he has spent the majority of his professional life. Joined on stage by the creative team of Claude-Michel Schonberg, Herbert Kretzmer and Alain Boublil each spoke of the "genius" of Victor Hugo, without whose original novel the piece could not have been written, as well as the strength of the working relationship between the four men, which has now existed for over 30 years.

As the confetti cannons fired it was this time the turn of cast members who have performed Les Miserables: Schools Edition to parade onto the floor of The O2 and, as flecks of red, white and blue rained down upon us, bring a memorable night to a close.

It is probably true to say that no one knew or predicted Les Miserables would have the longevity which it has enjoyed, and in that respect it seems slightly foolish to pooh-pooh Mackintosh's aspirations to be standing a stage aged 90 when the musical reaches its 50th birthday. I doubt the show will still be running continuously in the West End by that point, but it will surely still have a presence in the hearts of theatregoers the world over.