A work scheduled to last nearly two hours could be excused for starting with a long slow build up, but Havergal Brian’s massive Gothic Symphony (the longest symphony ever composed) bursts onto the scene with a brisk and bustling march-like flourish, contrasted briefly with a delicate violin solo that reminds us that this is very much an English composition. The rest of the first movement is musically intense as the tension is tightened in a series of harmonically complex climaxes, aided for the last few bars by the massive sound of the organ. The second movement is a rather sinister funereal march – not surprising considering the composition dates (1919 to 1927) in the aftermath of the war. It ends with a mournful growl from a bass clarinet that links to the insistent opening of third movement, a mood that soon collapses into a reflective passage before building into a strident march before it subsiding, gently, into the home key of D major. These three movements lasted 40 minutes, a reasonable length for an entire symphony.

For most composers, that would have been quite enough. But Brian’s continues with an enormous three movement choral Te Deum, lasting just over an hour, and using an orchestra nearly double the size. There are about 200 players, with four separate brass orchestras (in the side stalls), around 82 strings, 32 wind, 48 brass (24 side stage, eight in the gods,), 6 timpanists (playing 24 timpani), 18 percussionists, organ, plus the singers. A minimum of 500 adults and 100 children were specified, with 4 soloists, but the BBC provided over 800 singers.

The children’s choirs open Part Two with a chant-like invocation of the Te Deum, forming the melodic kernel of the whole movement. The work continues episodically, the tonality slowly shifting up from D to E, with lengthy passages for the singers alone (with the occasional pitch drop). The fifth movement, Judex crederis, opens with a capella choirs and an off-stage soprano and leads to the aural climax of the entire work when all four brass bands burst in, leading to an enormous climax. From where I was sitting, the massive bright red thunder machine (specially constructed for this performance, and like a giant tumble dryer) even managed its own lightening-flash effects, courtesy of the spotlight reflections. The final movement starts with a plaintive oboe solo and an extended tenor solo. It includes a magnificent jazz-like march with eight unison clarinets over a rattly percussion beat leading to a passage where the choirs sing to ‘Ah’ and ‘La la la’ as, “day by day” they “magnify thee” – this outburst of praise in the central part of the last movement was one of the highlights for me. Despite some very positive twists to the music, the end, when it comes, falls back into the bleak and despairing mood of earlier parts of the work with an extended bass solo, a short sotto voce double fugue, an angry outburst from percussion, brass and choir and an elegiac cello and oboe melody. The last three bars are given, magically and rather movingly, to the hushed a capella choir.

Brian takes no prisoners in his demands on the musicians. His writing is complex and difficult to play and sing. I know – I have tried, courtesy of an excellent Proms Plus Sing event earlier in the day. Within moments of starting to sing, the basses leap up to a top F# and, at the end, they hold bottom E for five long bars. The text underlay is awkward and there are some mind-boggling chromatic passages to negotiate. The instrumental writing is not comfortable and there are many moments of extraordinary virtuosity, notably from the xylophone. Martyn Brabbins did an amazing job in controlling the massed forces.

In musical-historical terms, this extraordinary work manages to look both forward and back, setting itself within the pan-European late romantic tradition but with tantalising foretastes of the musical world to come. Within the first 6 minutes we can glimpse Strauss, Mahler, Vaughan Williams, Bruckner, Nielsen, and Delius - in the choral second part we can add composers as varied as Tallis and Varèse. But this is no pastiche. Amazingly, this was Brian’s first symphony, although it was not performed until 1961. He went on to write another 31 symphonies and five completed operas. Not bad for a working class lad from Stoke-on-Trent who left school at 12.

Havergal Brian quotes Goethe's Faust in the score, "Whoever strives with all his might, that man we can redeem". On this occasion, the performers, the BBC, the entire audience (the concert sold out within hours) and, indeed, Havergal Brian himself, can justifiably feel thoroughly redeemed. The logistics of this work suggest that few people will have the chance of ever hearing it live again. The available recordings are poor and inaccurate, so it is vital that this BBC recording is eventually released - something that the indefatigable Havergal Brian Society are probably already working on.