Before the concert began, Yannick Nézet-Séguin gave a short introductory speech that, in effect, would have the Royal Festival Hall consecrated for the evening as a place of worship. He spoke of Bruckner’s deep Catholic faith, and how the programme was constructed to reflect that, with a symphony dedicated ‘To dear God’, and observing Bruckner’s last wish for the symphony: that his Te Deum be used as the finale in the event that he failed to complete it. The concert was to commence with the gradual Christus factus est, composed about the same time as the Te Deum. We were to listen to the whole sequence in silence - and, indeed, we did.

The London Philharmonic Choir sang the unaccompanied motet from memory. The words tell of Christ’s suffering on our behalf, for which God bestowed upon him ‘the name above all names’. It begins in D minor and in its short duration moves through a dramatic series of harmonic and dynamic changes, to end very slow and very quiet in a peaceful D major - at which point the London Philharmonic strings raised their bows to their instruments to create the shimmering pianissimo tremolo that opens the symphony. Then the horns began their misty exploration of the D minor triad. It was a moment of breathtaking magic and it ushered in a beautifully moulded opening paragraph, rising to the thundering statement of the implacable main theme, with its massive falling octaves and slithering chromatic triplet.

The other extraordinary transition created by the conjunction of three normally independent works came at the end of the three completed movements of the symphony. The dissonant enormity that constitutes the shattering climax of the Adagio was followed by deathly silence, after which the movement wound down through falling, world-weary tones on Wagner tubas, ultimately to the final held E major chord on horns, Wagner tubas, trombones: four bars that seemed to last for ever and ever, as though the LPO brass had infinite lung capacity. Then there was quiet, a silence that Nézet-Séguin described after the concert as being like purgatory: after Bruckner’s ‘farewell to life’ (the composer’s own description of the falling Wagner tuba chorale earlier in the movement) and the desolate negation of that dissonant climax, the conductor was called up to have faith enough to give ‘the biggest upbeat of his life’ to bring in the blazing C major fortissimo tutti affirmation of the Te Deum. It was quite brutal, and effectively swept away all the doubt and disturbance that had gone before - and was the total antithesis of the opening of the final movement that Bruckner was working on till the day he died. This unfinished movement creeps in quietly with a pianissimo tremolo on timpani before exploring further frightening, unsettled and obsessive motives; the planned affirmative close is either lost or unwritten.

As a programme this was an extraordinary event, and very powerful indeed, bringing a standing ovation from much of the audience who had sat mostly silently for nearly two hours without a break. It is often claimed that using the Te Deum as a finale to the symphony cannot work because it is in the wrong key, it is differently orchestrated, it’s composed in a different style: that it’s a desperate and unworkable solution born of the extremity of Bruckner’s final illness. What this concert showed was that it does work: not as an integrated symphonic finale to the work, but rather as a reflection on the unfinished symphony, a celebration of the faith and musical life of the composer who died in the course of its composition.

The whole project, and Nézet-Séguin’s obvious conviction and commitment, swept one along. The LPO’s playing was first-class, the choir tremendous, the four soloists superb. But there was much in the interpretation that took risks to their limit, and possibly beyond. At times, as the Adagio got slower and slower, Bruckner very reluctantly made his farewell to life; it was only the thought that the Te Deum would eventually arrive that sustained my own will to live. Similarly, the first movement second theme group was milked like an Adagio all of its own, dripping with sentiment, but ravishingly played and full of expressive rubato. The Scherzo was wonderfully fast, the pizzicato motive on violins with a neat crescendo to the top of the phrase, the great thumping main theme storming indomitably and at speed across the landscape, the trombones occasionally sounding through the texture with demonic growling and snarling. At this tempo the solos of the oboe and clarinet sounded like the chirruping of devils. The trio was equally breakneck and nightmarish - any faster and the virtuosity of flute and clarinet would have been taxing beyond human capability in their mad little semiquaver accompaniment. It was a performance of extremes and in no way confined by any straitjacket of monumental gravitas or mature reflection.

If the Te Deum took up anything from the symphony, then perhaps it was the sheer rhythmic energy of the Scherzo, a nightmare there transformed now into a joyful song of praise. The repetitive string motive - falling fourth and fifth - which Bruckner was to use again in the finale he never completed, was perhaps not as strongly and clearly articulated by the strings as it can be when the opening burst upon us, but on the whole this was a fabulous and colourful performance. Christine Brewer led the soloists in ‘Tibi omnes angeli’ with bell-like clarity, and Toby Spence’s ‘Te ergo quaesumus’ and ‘Salvum fac populum’ accomplished a stirring crescendo, from the quiet devotional openings, rising to heartfelt forte call on God for help. If there was any lingering darkness from the dissonant D minor symphony, then the long crescendo, ‘Non confundar in aeternum’, to triple forte with trumpet fanfares and high Cs from the sopranos, must have transformed it all into blazing light.

What a courageous and thoroughly admirable venture on the part of the LPO and Nézet-Séguin: a concert devoted entirely to Bruckner, a long concert without an interval, a very serious concert - but it paid off handsomely! And whatever doubts one might have about aspects of interpretation when considered in the cold light of day, on the night this was a mighty and unforgettable performance of these works that carried all before it.