The combination of the London Symphony Orchestra and Daniel Harding is a familiar enough sight at the Barbican and there have been a number of notable and memorable collaborations this year, not least a fabulous Beethoven Violin Concerto (with Christian Tetzlaff) back in May. On Thursday night it was Beethoven again, this time his Piano Concerto no. 3 in C minor and a completed version (from 2012) of the great musical torso that is Bruckner’s Symphony no. 9 in D minor, and here given its London première.

In the Beethoven, Maria João Pires was a commanding soloist. At 71, she still produces a wonderfully pure, crystalline tone and can also pile on plenty of muscle as she did for the piano’s opening flourish in the concerto’s first movement. She’s a joy to watch, a compact and undemonstrative figure without any self-regard or flamboyance and, unlike certain pianists recently performing in London, a model of restraint. On the podium, Harding created an efficient and tidy account, his well-behaved opening Allegro con brio neatly underlining the work’s Mozartian associations. Hard sticks from the timpanist, prominent woodwind and delicate, sometimes feather-light strings suggested the influence of period-instrument performance. Occasionally this performance was all too reined in, but beautifully so in the development section where oboe and bassoon were especially ear-catching.

The slow movement was lovingly crafted, with Pires an expressive poet, languorous in the long-breathed phrases, and knowing just when to linger and when to move forward. Where the finale had more bite than humour, its brief fugato section showed off the string section to impressive effect. Pires provided engagement and energy throughout, and was joined afterwards by Harding for Grieg’s Solveig’s Song. As encores go this was no party piece but afforded further evidence of her eloquence.

And so to Bruckner: the long span of the opening movement was mostly well-judged although there was little misterioso in its opening paragraph and the weight of those gargantuan climaxes never quite thrilled. No matter how technically assured Harding was, his elegant gestures also failed to draw from his string players that luminous tone essential for Bruckner’s lyricism, and passages of spiritual radiance felt unloved. Things considerably improved in the Scherzo, with meticulous pizzicato in its opening bars and with those thunderous unison figures later adding much to the excitement. Will-o-the-wisp strings in the Mendelssohnian trio were notably elfin-like. Harding had a sure sense of the Adagio’s momentum, which culminated in an intensely wrought coda, the players on terrific form.

But what of the incomplete fourth movement, left unfinished when the composer died in October 1896? This latest Herculean effort (one of at least seven made in the last 50 years) was compiled by a scholarly foursome, Samale-Phillips-Cohrs-Mazzuca and has been vigorously applauded by some, but whether it will be attached regularly to the more familiar torso we know and admire remains to be seen. Harding and his LSO forces put up a good case for it with some fine playing that included stylish contributions from the horn section (with four Wagner tubas) delivering its noble chorale theme. But despite a magnificent closing section, this 22-minute movement, laden with rhetorical gestures, seemed overly long. Who knows what its shelf-life will be, and judging from three overheard comments it may last only as a curiosity.