With one hushed pianissimo chord, it was over. As Daniel Barenboim leapt up from the piano, so 3,000 people in the Festival Hall were on their feet too, and roaring.

Even those with long memories can recall nothing like this since the era of Rubinstein, Horowitz or Richter, piano legends who filled this hall three decades or more ago.

This ovation marked the end of Barenboim's eight-concert, 32 piano sonata marathon, which has held musical London gripped for a fortnight.

Our heartfelt applause was in praise of two great musicians, both in their own time recognised as ardent champions of the brotherhood of man.

The first, there on stage in front of us, small and hot, dabbing sweat off his face, a pianist whose virtuosity has been evident since childhood but who only now, aged 65, has realised his astonishing potential to the absolute maximum.

The second, Beethoven himself, who needs no endorsement but whose revolutionary genius can never have been more vividly, or persuasively, or courageously displayed.

So many words have now been spilt over Barenboim's playing that there's little to add.

We can say that his account of the near-hackneyed "Moonlight" Sonata, with its surprise extra repeat and wild air of improvisation, sounded as radical as Stravinksy.

Or that in Opus 110, the lurch from plaintive song into explosive three-voice fugue hit us like a tornado, as if Barenboim had suddenly hurled his Steinway - all 12,000 parts of it, wood, felt, steel, nickel and all - into a whirlwind so violent than either man or instrument seemed sure to combust.

There's a sense in which, at this level, excellence cannot be controversial. The only sniping was last week's media spat over his refusal to let the BBC in to record - entirely understandable given the musical risks he was taking, which microphones or cameras might have inhibited.

This was about being there, about witnessing an historic event which no one present will forget.

The same faces came night after night. Strangers struck up conversation on the Tube going home. Even the loquacious were struck dumb.

One woman, with hearing aids in both ears, joined the free live relay in the foyer "just to be there" though unable to hear much. If she hoped to draw solace from a composer who charted the torment of his creeping deafness in these 32 masterpieces, she was surely rewarded.

Nowhere is the music more sublime than at the close of Opus 111, the final summation. Here especially, Barenboim held us transfixed.

At the end, he closed the piano lid as if to say, no more. If proof of the vitality of live music making were ever needed, this was it.