The Milton Court concert hall and theatre building is a splendid enhancement of the Guildhall's and London's performance facilities. It strikes you immediately as a friendly environment, and from up in the circle, the acoustic seemed to me a model of clarity. The orchestra is used by Prokofiev in his Third Piano Concerto with considerable restraint – indeed, for a lot of the time the brass players sat at the back looking as though they were just there to wait for the Bruckner – but it felt as though the small hall was at its limits in coping with the full treble fortes of Bruckner's brassy tuttis in the Third Symphony. No doubt as conductors and players become more familiar with the venue they will refine their response to the hall.

Writer Graham Greene divided his works into "entertainments" and "novels", the serious literary works, and this programme of Prokofiev and Bruckner might at first sight seem to divide itself similarly, because for all its wit and sarcasm, colour and frenetic virtuosity, Prokofiev's concerto is an entertainment – of the first order. When the woodwind delivers a wild, ironic, near-screeching motif it is not to be heard like something out of Mahler or Shostakovich, an agonised response to the existential abyss, but more often than not a witty variation on the theme, a jazz-inflected cleverness, there to delight and entertain. And certainly this performance by Nikolai Demidenko was astounding in its sheer virtuosity, and the delight and entertainment that that offered.

Kensington Symphony Orchestra, "one of the finest amateur orchestras in the UK", didn't seem for a moment fazed by the difficulties the composer presented, and if perhaps the wit could on occasion have been just a touch more biting, it only served to foreground the sharp precision of the soloist's articulation of Prokofiev's quirky themes and insistent rhythms. And it all came to a fine "big tune" climax towards the end of the third movement with the glorious strings swooping up and down as Demidenko hammered away at the upper-register ornamentation, and the movement that Prokofiev called an "argument" between soloist and orchestra came to a close in stunning unanimity. And as if that weren't enough, Demidenko then gave as an encore – Medtner's La Campanella – a piece with a repeated descending figure in the bass subject to no end of virtuoso embellishment, which closed his breathtaking contribution to the evening.

The Bruckner was far less successful. Russell Keable chose to conduct the very first version of this symphony. It's still quite rare to hear this first version, the one that Bruckner actually showed to Wagner who then accepted its dedication, and usually it makes a good case for Bruckner's first thoughts being his most convincing. But tonight the conductor seems to have decided to treat it like an ordinary classical symphony and kick off with a good old symphonic allegro. Bruckner's marking "measured and mysterious" was ignored and the misty atmospheric opening through which the trumpet sounds the opening theme sounded more like an urgent Prokofiev ostinato. It's not that the symphony cannot work taken at this speed, but it means that one dimension of the Bruckenerian experience – its measured spaciousness – is squeezed out, and must needs be replaced by something equally interesting. When the Heidelberg Philharmonic performed this version, even quicker than the Kensington Symphony Orchestra tonight, it was the sheer energy and ferocity of the playing, and the virtuosity of the orchestra in keeping up with it, that made the performance a great one; but there was no such interest to compensate for the lack of mystery in Keable's view of the work.

Even so, the first two movements worked quite well, and the consistent tempo relationships between the themes gave the movements an effective formal cogency. The tutti climaxes were always impressive, though the acoustic or the orchestral balance was such that the inner voices were often lost. The moment of calm at the opening of the development, when the solo horn plays pianissimo octave drops above pianissimo strings, was nicely done although over all too soon, but the movement's closing pages were very effective. The slow movement, marked to be a solemn adagio, strained at the limits of that description, but the tender second theme was very affectingly played by the violas and then cellos. But the second theme of that group, a halting theme marked "misterioso" and triple piano, was neither of those things. Indeed, the quieter end of the dynamic range was rarely effectively observed throughout this performance. The Wagnerian climax, with trombones in fine form, sounded tremendous.

The man beside me, unsolicited, remarked there had been no tunes so far, which didn't bode well for this performance's effectiveness in winning new friends for Bruckner's symphony. But in the Scherzo and Finale I fear things deteriorated. There needed to be more precision and togetherness in the strings, more space for the stamping rhythms of the Scherzo to register – though the accents of the trio's dance were attractively weighted. And come the finale, once again very fast (but at least here Bruckner's marking is allegro), the whole thing just became unutterably noisy. The polka of the second subject on violins was undermined by both its speed and the orchestral balance so that the full contour of the theme was rarely to be heard, even by those of us who know it well. There was one really special moment, when the four horns play a chorale, otherwise unaccompanied, towards the end of the development, to be taken up by woodwind. This was very beautifully done, as was the coda – a moment where Keable seemed to allow space for a little grandiloquence – and this close, which sometimes lacks the requisite finality in this version, at last gave us a glimpse of the visionary inspiration that lies behind this mighty symphony.

Kensington Symphony Orchestra, at Guildhall School of Music & Drama: Milton Court Concert HallKen Ward reviews Demidenko and Kensington Symphony Orchestra in Prokofiev's Piano Concerto No 3 and Bruckner Symphony No 3 under Russell Keable