A packed house… a delirious fanbase calling for their favourite songs and then for more… a collective sign afterwards… and, an obvious sense amongst a clear majority of those present that they’d just seen something special.

All reactions I fully expected for Anais Mitchell’s first London shows after the release of her masterpiece, ‘Hadestown’. A studio recording of the songs from her stage show, it merged spine-chilling ballads with stomping show tunes, delicate string parts with bar-room blues - and all in the company of some of the finest vocalists in American folk music; Ani DiFranco, Justin Vernon, Greg Brown and Ben Knox Miller.

It’s a classic album - not just a ‘buzz’ release that’ll be confined to dusty shelves in six months’ time, but a real classic. And its not just me that thinks so: “It’s nothing short of incredible”, 'NME'; “Nothing short of awe-inspiring”, 'Drowned In Sound'; “Something joyful and witty that yields more with every listen”, 'The Guardian'.

So, it seems only reasonable to ask why this fantastic, triumphant performance took place in the 12 Bar (a charming venue, and one that I fully intend to return to, but one with barely enough room for 60 people to watch the music comfortably) and not at the Royal Festival Hall or the Barbican. I’ve seen Anais Mitchell three times in the last 18 months, and each time, I’ve left assuming that this would be the last time I’d see her in a small bar-room venue. Maybe next time I’ll be right.

For now, I’ll enjoy being part of a very lucky few - for this was a fantastic performance. Mitchell does not strike me as a natural performer, seeming slightly nervous and unable to stand still on stage. But she has a rare gift of allowing a receptive audience to be carried along by her music, as time appears to stand still while she songs. It is not hard to see why - a combination of literate lyrics for which you strain the ear to catch properly, intricate finger-picked guitar that allows the songs to take unexpected twists and turns and soaring melodies that it is hard not to sing along with, even in a tiny, hushed venue.

This was the first chance we’d had to hear the 'Hadestown' songs live having already absorbed them on record. Having ushered a friend on stage to sing the duetted parts, they were a riot - affirmation for what will surely end up as the album of the year. Mitchell’s experience and class as a solo performer ably compensates.

But, this show was also a reminder that Mitchell was a class act long before she recruited her famous friends and gathered in praise from the national media. The other half of tonight’s set came from ‘The Brightness’, released in 2007 and tragically under-appreciated in this country. Traditionally in approach, slenderly arranged and simply produced, it lives and dies by the strength of the songwriting. Time and again, I go back to this album and it always feels like a present enthusiasm, and not a nostalgia trip.

To those longstanding fans present tonight, this album has clearly been memorised and absorbed. After consenting to a request to play ‘Song For the Magi’, but professing not to remember the words, Anais is lead through it by three people standing to the right of the stage.

The enduring image of this album is of a deeply imaginative songwriter who has deeply touched a handful of devoted fans. Surely, surely, in time she will establish herself as one of the most admired folksingers on the planet? She is certainly one of the best.