Prom 5: LSO/Haitink, Royal Albert Hall, London

Some concerts develop a momentum before they've begun. The London Symphony Orchestra's Prom with Bernard Haitink conducting Mahler's Ninth Symphony was one such. With all of musical London seemingly heading into the hall, the buzz was palpable, and it heralded an incomparable evening.

Haitink, who has just celebrated his 80th birthday, has enjoyed a half-century of special association with Mahler. Although he's one of the world's most versatile conductors, it has been Mahler who's arguably drawn from him his finest work. This was his first concert since undergoing an operation on his back two months ago, and the venerable Dutch maestro looked frail and slight, alternately standing and sitting through the gargantuan symphony. Usually when conductors reach 60, they become "distinguished"; around 70, they're regarded as "great"; but past 80, they can be virtually sanctified. If any of them has ever deserved that status, it was Haitink, here, tonight.

In this, his last completed symphony, Mahler – devastated by his daughter's death, with his marriage under intolerable strain and a heart condition threatening him with premature death – was facing head on the fragility of his physical and emotional existence. Mahler laid his spirit bare in a poem to the wonder and pain of life, its emotions so personal that you almost wonder why he didn't choose an equally intimate form for them, rather than an outsize symphony orchestra.

The paradox of complete intimacy conveyed on a giant scale is a tad boggling, but especially in an interpretation as rare as this, in which every ultra-controlled violin bow, every piercing high trumpet and every heart-stopping solo from string principal or woodwind served Mahler's purpose – his golden refulgence, biting irony, the all-too-prophetic destruction from within. Special mentions roundly deserved for first horn David Pyatt, first trumpet Roderick Franks, lead cellist Tim Hugh and concertmaster Gordan Nikolitch. No phrase contained a moment of insincerity; the valedictory work, unfolding as expansively as it deserves, emerged stronger for the way that Haitink focused on its delicacy and the vulnerability of the soul it reveals.

The Royal Albert Hall has an unflattering acoustic, so it was testimony to the concentration of all concerned that the skittering rhythms of the ländlers in the second movement emerged with such clarity. Tempi were slower than some might have wished, but the articulation and emotional pacing justified those choices. The long-sustained hush of the final movement must have terrified the violins – but if so, you wouldn't have known it from their tone.

Indeed, the LSO can never have sounded more ideal: the string sections each played as one instrument. And throughout, a hundred people on stage offered an experience akin to chamber music to an audience of six thousand who could almost have been sitting together in Mahler's living room – and later wandered out into the Kensington sunset, marvelling and speechless, knowing they'd never forget this night.